KR102498689B1 - Adhesive sheets, display devices and laminates - Google Patents

Abstract

The present invention provides a pressure-sensitive adhesive sheet capable of exhibiting good hiding properties even against adherends to which processing has been applied to the surface to which the pressure-sensitive adhesive sheet is applied. A pressure-sensitive adhesive sheet including a pressure-sensitive adhesive layer is provided. The pressure-sensitive adhesive layer has a light transmittance of 20% or less, and L ^* defined in the L ^* a ^* b ^* color system is 20 or more and 70 or less.

Description

Adhesive sheets, display devices and laminates

The present invention relates to an adhesive sheet, a display device, and a laminate.

This application claims priority based on Japanese Patent Application No. 2020-146096 filed on August 31, 2020 and Japanese Patent Application No. 2021-007761 filed on January 21, 2021, and the The entire contents are incorporated herein by reference.

In general, pressure-sensitive adhesives (also referred to as pressure-sensitive adhesives. The same applies hereinafter) exhibit a soft solid (viscoelastic) state in a temperature range around room temperature, and have a property of easily adhering to an adherend by pressure. Taking advantage of such properties, adhesives are widely used in various applications, for example, for the purpose of bonding, fixing, or protecting members in portable electronic devices such as mobile phones. For example, for the purpose of preventing light leakage from a light source such as a backlight module of a liquid crystal display device in a portable electronic device such as a mobile phone or a self-light emitting element such as organic EL (electroluminescence), an adhesive containing a light-shielding adhesive layer sheet is used. In addition, for the purpose of concealing the adherend, adjusting the appearance of the adherend over the adhesive sheet (for example, suppressing uneven appearance), design, etc., an adhesive sheet having predetermined light blocking or photosensitivity is used. Patent Document 1 can be cited as a document related to this type of technology.

Japanese Unexamined Patent Publication No. 2020-37657

A light-shielding adhesive sheet used for the purpose of concealing an adherend or adjusting appearance achieves the purpose of concealment or the like by uniformly covering the entire visual side surface of an adherend. For example, since the display portion of various electronic devices is visible to the user's eyes, appearances having higher homogeneity are required. In the display portion of such an electronic device, a light-shielding adhesive sheet can be used for concealing a metal member disposed on the back side of an organic EL panel or the like, but even for such a light-blocking adhesive sheet, the uniformity of appearance beyond the adhesive sheet It is preferable to conceal the said metal member while maintaining. However, if a process such as perforation is applied to the adhesive sheet sticking surface of a metal member as an adherend, when the adherend is viewed through the adhesive sheet, due to a difference in color between the light-shielding adhesive sheet and the adherend, the processed portion of the adherend Contrast with the periphery is conspicuous, and there are cases where uniform concealment of the adherend is impaired.

The present invention was created in view of the above circumstances, and an object of the present invention is to provide a pressure-sensitive adhesive sheet capable of exhibiting good hiding properties even against an adherend having a processed surface on which the pressure-sensitive adhesive sheet is attached. Another related object is to provide a display device and a laminate including the pressure-sensitive adhesive sheet.

According to this specification, a pressure-sensitive adhesive sheet including a pressure-sensitive adhesive layer is provided. The pressure-sensitive adhesive layer has a light transmittance of 20% or less, and L ^* defined in the L ^* a ^* b ^* color system is 20 or more and 70 or less. According to the configuration described above, since the pressure-sensitive adhesive layer has limited light transmittance, the adherend can be concealed. In addition, the PSA sheet containing the PSA layer having L ^* defined in the L ^* a ^* b ^* color system is 20 or more and 70 or less, even when the PSA sheet sticking surface of the adherend is processed, the PSA sheet does not cover unevenly. is suppressed That is, according to the above-mentioned PSA sheet, it is possible to exhibit good concealment performance in which concealment non-uniformity is suppressed even for an adherend to which processing has been applied to the PSA sheet sticking surface.

In some preferred aspects, in the pressure-sensitive adhesive layer, both a ^* and b ^* defined in the L ^* a ^* b ^* color system are within a range of -10 or more and +10 or less. The fact that a ^* and b ^* defined in the L ^* a ^* b ^* color system are relatively small values means that the L ^* dependence of the color tone of the pressure-sensitive adhesive layer is high. In the pressure-sensitive adhesive layer having such a color tone, the effect of setting L ^* within a predetermined range is preferably exhibited.

In some preferred aspects, the pressure-sensitive adhesive layer contains a black colorant as the first colorant and a metal oxide as the second colorant. As a colorant, by using a black colorant and a metal oxide together, the light transmittance of a predetermined value or less and the lightness (L ^* ) within a predetermined range are preferably compatible.

In some preferred aspects, the content of the metal oxide in the pressure-sensitive adhesive layer is 1% by weight or more and 6% by weight or less. By setting the amount of the metal oxide to 1% by weight or more and 6% by weight or less, L ^* within a predetermined range can be preferably realized while achieving a light transmittance of a predetermined value or less. In addition, when the content of the metal oxide is 6% by weight or less, it is easy to maintain adhesive properties such as adhesive force.

In some preferred embodiments, the content of the black colorant in the pressure-sensitive adhesive layer is less than 2% by weight. By restricting the content of the black colorant in the pressure-sensitive adhesive layer to less than 2% by weight, the light transmittance of a predetermined value or less and L ^* within a predetermined range can be preferably compatible.

In some preferred embodiments, the weight ratio (C1/C2) of the amount of the first colorant (C1) and the amount of the second colorant (C2) is in the range of 0.01 to 0.30. By setting the usage ratio of the first colorant and the second colorant within the above range, the light transmittance of a predetermined value or less and the L ^* within the predetermined range can be favorably compatible.

In some preferred embodiments, the content of the colorant in the pressure-sensitive adhesive layer is 1% by weight or more and 10% by weight or less. By adding a colorant to the pressure-sensitive adhesive layer in an amount of 1 to 10% by weight in the pressure-sensitive adhesive layer, the light transmittance of a predetermined value or less and L ^* within a predetermined range can be preferably compatible. In addition, when the amount of the coloring agent is 10% by weight or less, it is easy to maintain adhesive properties such as adhesive strength.

The pressure-sensitive adhesive layer disclosed herein may be an acrylic pressure-sensitive adhesive layer containing an acrylic polymer as a base polymer. In a configuration including an acrylic pressure-sensitive adhesive layer, the technique disclosed herein is preferably implemented.

In some preferred embodiments, the thickness of the pressure-sensitive adhesive layer is in the range of 10 to 50 μm. By setting the thickness of the pressure-sensitive adhesive layer to 10 µm or more, light transmittance of a predetermined value or less and L ^* within a predetermined range can be preferably realized. In addition, there is a tendency to realize desired adhesive properties easily. By making the thickness of an adhesive layer into 50 micrometers or less, it can become what respond|corresponded well to the request of thinning and weight reduction.

A pressure-sensitive adhesive sheet according to some preferred embodiments is a substrate-free double-sided adhesive pressure-sensitive adhesive sheet including the pressure-sensitive adhesive layer. Substrate-free double-sided pressure sensitive adhesive sheet can be reduced in thickness to the extent that it does not have a base material, and can contribute to miniaturization and space saving of products to which the double-sided pressure sensitive adhesive sheet is applied. In addition, according to the base-free pressure-sensitive adhesive sheet, the effects of the pressure-sensitive adhesive layer such as adhesive strength and impact resistance can be expressed to the maximum extent.

The pressure-sensitive adhesive sheet is preferably used in an aspect that is affixed to a region including a processed portion of a processed metal member. An adhesive sheet containing an adhesive layer having a light transmittance of 20% or less and an L ^* of 20 or more and 70 or less is adhered to the surface of a metal member subjected to processing such as perforation, and the adherend (metal member) is viewed through the adhesive sheet. In this case, the contrast between the processed portion of the adherend and its peripheral portion is less conspicuous, and the concealment of the adherend is less likely to be impaired. Since the PSA sheet disclosed herein can exhibit good hiding properties regardless of whether or not an adherend is processed, there are few restrictions on where the PSA sheet can be applied, and its usability is excellent. Preferred examples of the metal member include a metal member (typically a stainless steel member or an aluminum member) having a surface to which the adhesive sheet is applied made of stainless steel or aluminum.

The adhesive sheet disclosed herein may be preferably used to bond metal members of portable electronic devices. For example, a portable electronic device may have a part visible to the user's eyes, so that an appearance having higher homogeneity may be required. By using the pressure-sensitive adhesive sheet disclosed herein for concealment of a metal member used for such a part, an appearance having high homogeneity with little concealment unevenness can be imparted.

1 is a cross-sectional view schematically showing one configuration example of an adhesive sheet.
Fig. 2 is a cross-sectional view schematically showing one configuration example of a laminate.
Fig. 3 is a schematic view of the laminate shown in Fig. 2 viewed from the second member side.
4 is an exploded perspective view schematically illustrating a configuration example of a display device.

Preferred embodiments of the present invention will be described below. In addition, matters necessary for the practice of the present invention other than those specifically mentioned in this specification can be understood by those skilled in the art based on the teachings for the practice of the invention described in this specification and common technical knowledge at the time of filing. The present invention can be practiced based on the contents disclosed in this specification and common technical knowledge in the related field. Note that in the following drawings, the same reference numerals are assigned to members and parts that perform the same functions in some cases, and overlapping explanations are omitted or simplified in some cases. In addition, the embodiments described in the drawings are modeled in order to clearly explain the present invention, and do not necessarily accurately represent the size or scale of products actually provided.

In this specification, 'adhesive', as described above, refers to a material that exhibits a soft solid (viscoelastic material) state in a temperature range around room temperature and has a property of easily adhering to an adherend by pressure. As defined in 'CA Dahlquist, "Adhesion: Fundamental and Practice", McLaren & Sons, (1966) P.143', the pressure-sensitive adhesive referred to herein is generally complex tensile modulus E ^* (1Hz) <10 ⁷ It may be a material having properties satisfying dyne/cm 2 (typically, a material having the above properties at 25° C.).

<Configuration example of adhesive sheet>

The PSA sheet disclosed herein may be a non-releasable PSA sheet with a base material including the PSA layer on one side or both sides of a non-releasable base material (supporting base material), or a non-removable PSA sheet in which the PSA layer is held by a release liner. It may be a base material pressure-sensitive adhesive sheet (ie, a pressure-sensitive adhesive sheet that does not contain a non-peelable base material). The concept of the pressure-sensitive adhesive sheet herein may include what is called an adhesive tape, an adhesive label, an adhesive film, and the like. In addition, the PSA sheet disclosed herein may be in the form of a roll or sheet. Alternatively, it may be a pressure-sensitive adhesive sheet processed into more diverse shapes.

A structural example of a double-sided adhesive type non-substrate adhesive sheet (substrate-free double-sided adhesive sheet) is shown in FIG. 1 . In the PSA sheet 1 shown in FIG. 1 , both surfaces 21A and 21B of the non-substrate PSA layer 21 (which are also the PSA surfaces 1A and 1B of the PSA sheet 1, respectively) contain at least the PSA. It has a structure in which the layer side is each protected by release liners 31 and 32 serving as release surfaces. Alternatively, the pressure-sensitive adhesive sheet has a configuration in which one surface (adhesive surface, first adhesive surface) of the base-free pressure-sensitive adhesive layer is protected by a release liner in which both surfaces are release surfaces, and when the pressure-sensitive adhesive sheet is wound, the pressure-sensitive adhesive layer By bringing the other surface (adhesive surface, second adhesive surface) into contact with the back surface of the release liner, the second adhesive surface of the pressure-sensitive adhesive layer may also be protected by the release liner. The technique disclosed herein can be preferably implemented in such a substrate-free form from the viewpoint of reducing the thickness of the pressure-sensitive adhesive sheet. The base material-free pressure-sensitive adhesive sheet is advantageous also in that it is easy to thin the layer and can exhibit the properties of the pressure-sensitive adhesive such as adhesive strength and impact resistance to the maximum. In addition, the light transmittance of the pressure-sensitive adhesive layer 21 is limited to 20% or less as will be described later.

<Characteristics of pressure-sensitive adhesive layer>

(light transmittance)

The pressure-sensitive adhesive layer constituting the pressure-sensitive adhesive sheet disclosed herein has a light transmittance of 20% or less. A PSA sheet containing such an PSA layer is suitable for concealing the adherend and adjusting the appearance of the adherend through the PSA sheet (for example, suppression of uneven appearance), and can impart design. The light transmittance of the pressure-sensitive adhesive layer may be 18% or less, and in some preferred embodiments, the light transmittance of the pressure-sensitive adhesive layer may be less than 12% or less than 10%. The lower the light transmittance, the better the hiding property. The lower limit of the light transmittance is not particularly limited, and may be substantially 0%, ie, less than the detection limit, or may be 0.05% or more from the viewpoint of compatibility with the light reflectance described later. 0.1% or more may be sufficient, 1.0% or more may be sufficient, 2.0% or more may be sufficient, and 5.0% or more may be sufficient. In some aspects, the light transmittance of the pressure-sensitive adhesive layer may be 8.0% or more. By having a certain degree of light transmittance, the adherend can be appropriately concealed, the appearance of the adherend (for example, a metal material) can be adjusted, or a design that retains the texture of the adherend can be imparted. Further, in the configuration including the pressure-sensitive adhesive layer having a light transmittance equal to or greater than the predetermined value, in other words, in the pressure-sensitive adhesive sheet including the pressure-sensitive adhesive layer that transmits light to some extent, L ^* of the pressure-sensitive adhesive layer described later is in the range of 20 or more and 70 or less. The effect of (e.g., suppression of concealment non-uniformity by setting the color tone of the same system as the adherend) is preferably exhibited. Further, a pressure-sensitive adhesive layer having moderate light transmittance is also preferable from the viewpoints of maintenance of adhesive properties, productivity, and the like.

The light transmittance of the pressure-sensitive adhesive layer can be measured by the method described in Examples described later. The light transmittance of the pressure-sensitive adhesive layer can be adjusted according to the pressure-sensitive adhesive-containing component (for example, the type or amount of colorant (preferably black colorant) used), the thickness of the pressure-sensitive adhesive layer, and the like.

(L ^* a ^* b ^* colorimetric characteristics)

In addition, the pressure-sensitive adhesive layer has L ^* defined in the L ^* a ^* b ^* color system of 20 or more and 70 or less. The pressure-sensitive adhesive layer having a light transmittance of 20% or less and L ^* adjusted to 20 or more and 70 or less is compared to a pressure-sensitive adhesive layer having a light transmittance of 20% or less in which L ^* is not adjusted to the above range. Concealed by the pressure-sensitive adhesive sheet It tends to approach the color of the adherend. Accordingly, even when processing is applied to the surface to which the adhesive sheet is applied to the adherend, the contrast between the processed portion and its peripheral portion is less conspicuous, and unevenness in concealment by the adhesive sheet is suppressed. In addition, L ^* represents lightness in the L ^* a ^* b ^* color system. The L ^* may vary depending on the color of the adherend (eg, metal member), but in some embodiments, it is usually 50 or less, preferably 48 or less, more preferably 45 or less, still more preferably At least it is 42 or less. Further, the L ^* is preferably 30 or more, more preferably 35 or more, still more preferably 40 or more. For example, when the material constituting the adhesive sheet sticking surface of the adherend is stainless steel or aluminum, it is suitable to set it as the range of L ^* mentioned above. In some other aspects, L ^* is preferably 65 or less, may be 62 or less, 60 or less, 58 or less, or 56 or less (for example, 52 or less). In some of the other aspects described above, L ^* may be greater than 45, greater than 50, or greater than 54 (for example, greater than 55). According to such an aspect, the adherend can be satisfactorily concealed using the diffused light in the pressure-sensitive adhesive layer.

Although not particularly limited, the pressure-sensitive adhesive layer preferably has both a ^* and b ^* defined in the L ^* a ^* b ^* color system within a predetermined range. The fact that a ^* and b ^* defined in the L ^* a ^* b ^* color system are relatively small values means that the L ^* dependence of the color tone of the pressure-sensitive adhesive layer is high. In the pressure-sensitive adhesive layer having such a color tone, the effect of setting L ^* within a predetermined range is preferably exhibited. Further, in the pressure-sensitive adhesive layer in which L ^* is equal to or greater than a predetermined value, the fact that the chromaticities a ^* and b ^* are within a predetermined range means, for example, that a reddish or yellowish color is limited, and the color tone of the adherend or its peripheral members is reduced. easy to harmonize with From such a point of view, the a ^* is preferably -15 or more, preferably -10 or more, more preferably -5 or more, still more preferably -1 or more (eg -0.3 or more), and 15 or less is appropriate, preferably 10 or less, more preferably 5 or less, still more preferably 1 or less (for example, 0.3 or less). From the same point of view, the b ^* is preferably -15 or more, preferably -10 or more, more preferably -5 or more, even more preferably -3 or more (e.g. -2 or more), and also 15 The following is appropriate, preferably 10 or less, more preferably 5 or less, still more preferably 3 or less (for example, 2 or less).

Each value of L ^* a ^* b ^* of the pressure-sensitive adhesive layer can be measured by the method described in Examples described later. Each value of L ^* a ^* b ^* of the pressure-sensitive adhesive layer can be adjusted according to the pressure-sensitive adhesive-containing component (for example, the type or amount of colorant (eg, white colorant, preferably metal oxide)).

In the case of a double-sided pressure-sensitive adhesive sheet having adhesive surfaces on both sides, each value of L ^* a ^* b ^* on the surface of each pressure-sensitive adhesive layer (each adhesive surface, first adhesive surface, and second adhesive surface) may be the same or different. do. In an aspect in which the L ^* of each pressure-sensitive adhesive layer surface (each pressure-sensitive adhesive surface) of the double-sided pressure-sensitive adhesive sheet is different, one pressure-sensitive adhesive layer surface (eg, the first pressure-sensitive adhesive surface) only needs to have the above L ^* , and the other pressure-sensitive adhesive layer surface (eg, the second pressure-sensitive adhesive surface) L ^* of the surface) may be outside the range of 20 to 70.

(light reflectance)

Although not particularly limited, in some embodiments, it is appropriate that the light reflectance of the pressure-sensitive adhesive layer is 8.0% or higher. Although the amount of incident light is limited in the pressure-sensitive adhesive layer having limited light transmittance as described above, even in such a pressure-sensitive adhesive layer, the light entering the pressure-sensitive adhesive is refracted and scattered within the pressure-sensitive adhesive, thereby realizing higher precision optical control. There are times when things are difficult. In addition to limiting the light transmittance of the pressure-sensitive adhesive layer, the light reflectance on the surface of the pressure-sensitive adhesive layer is set to 8% or more to reflect light on the pressure-sensitive adhesive surface and reduce light entering the pressure-sensitive adhesive, thereby improving light blocking properties, photosensitivity, and high precision. Optical control is compatible. The light reflectance of the pressure-sensitive adhesive layer is preferably 9.0% or more, more preferably 10% or more, still more preferably 12% or more, and may be 14% or more (for example, 16% or more). In some embodiments, the light reflectance may be 18% or more, or 22% or more (for example, 25% or more). Since the upper limit of the light reflectance is set in an appropriate range in relation to the light transmittance, it is not limited to a specific range, and is, for example, less than 40%, may be 30% or less, may be 25% or less, may be 20% or less (for example, 15% or less).

The light reflectance of the pressure-sensitive adhesive layer can be measured by the method described in Examples described later. The light reflectance of the pressure-sensitive adhesive layer can be adjusted according to the pressure-sensitive adhesive-containing component (for example, the type or amount of colorant (preferably metal oxide)).

In the case of a double-sided pressure-sensitive adhesive sheet including adhesive surfaces on both sides, the light reflectance of the surface of each pressure-sensitive adhesive layer (each adhesive surface, first adhesive surface, and second adhesive surface) may be the same or different.

The relative relationship between the light transmittance and light reflectance of the pressure-sensitive adhesive layer is not particularly limited. From the viewpoint of better compatibility between the reduction in light transmittance and the reduction in the amount of incident light to the pressure-sensitive adhesive layer, for example, the ratio (R/T) of the light reflectance (R) to the light transmittance (T) of the pressure-sensitive adhesive layer is preferably 0.4 or more. It is preferably 0.5 or more, more preferably 1.0 or more, and may be 2.0 or more. Also, the upper limit of the ratio (R/T) may be about 10 or less, for example 5 or less. In an aspect in which a certain degree of light transmittance is required for the pressure-sensitive adhesive layer, the ratio (R/T) may be less than 3, may be less than 2, or may be less than 1.

<Adhesive layer>

(base polymer)

In the technique disclosed herein, the type of the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer is not particularly limited. The pressure-sensitive adhesive includes acrylic polymers, rubber-based polymers (natural rubber, synthetic rubber, mixtures thereof, etc.), polyester-based polymers, urethane-based polymers, polyether-based polymers, silicone-based polymers, and polyamide-based polymers that can be used in the field of pressure-sensitive adhesives. , One or two or more of various rubbery polymers such as fluorine-based polymers may be included as an adhesive polymer (meaning a structural polymer that forms an adhesive, hereinafter also referred to as a 'base polymer'). From the standpoint of adhesive performance, cost, etc., an adhesive containing an acrylic polymer or a rubber polymer as a base polymer can be preferably employed. Among them, an adhesive having an acrylic polymer as a base polymer (acrylic adhesive) is preferable. The technique disclosed herein is preferably implemented in an aspect using an acrylic pressure-sensitive adhesive.

Hereinafter, a pressure-sensitive adhesive layer made of an acrylic pressure-sensitive adhesive, that is, a pressure-sensitive adhesive sheet including an acrylic pressure-sensitive adhesive layer will be mainly described, but the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet disclosed herein is not limited to one made of an acrylic pressure-sensitive adhesive.

In addition, the "base polymer" of an adhesive refers to the main component of the rubber-like polymer contained in the said adhesive, and other than this, it is not interpreted restrictively at all. The rubbery polymer refers to a polymer that exhibits rubber elasticity in a temperature range around room temperature. In addition, in this specification, 'main component' refers to a component contained in excess of 50% by weight, unless otherwise specified.

In addition, an "acrylic polymer" refers to a polymer comprising a monomer unit derived from a monomer having at least one (meth)acryloyl group in one molecule as a monomer unit constituting the polymer. Hereinafter, a monomer having at least one (meth)acryloyl group in one molecule is also referred to as an 'acrylic monomer'. Therefore, the acrylic polymer in this specification is defined as a polymer containing a monomer unit derived from an acrylic monomer. As a typical example of the acrylic polymer, an acrylic polymer in which the ratio of the acrylic monomer is greater than 50% by weight among all the monomer components used in the synthesis of the acrylic polymer is exemplified.

In addition, "(meth)acryloyl" is the meaning which points out acryloyl and methacryloyl comprehensively. Similarly, '(meth)acrylate' refers to acrylate and methacrylate, and '(meth)acryl' refers to acryl and methacryl, respectively.

(Acrylic polymer)

As the acrylic polymer in the technology disclosed herein, for example, a monomer that contains an alkyl (meth)acrylate as a main monomer and may further contain a sub-monomer having copolymerizability with the main monomer. Polymers of raw materials are preferred. Here, the main monomer refers to a component that accounts for more than 50% by weight of the monomer composition in the monomer raw material.

As an alkyl (meth)acrylate, the compound represented by following formula (1) can be used suitably, for example.

CH ₂ =C(R ¹ )COOR ² (1)

Here, R ¹ in the formula (1) is a hydrogen atom or a methyl group. In addition, R ² is It is a chain alkyl group of 1 to 20 carbon atoms. Hereinafter, such a range of carbon atoms may be expressed as 'C _1-20 '. From the viewpoint of the storage modulus of the pressure-sensitive adhesive, etc., R ² is An alkyl (meth)acrylate, which is a chain alkyl group of C _1-14 (eg C _1-10 , typically C _4-8 ), is suitably used as the main monomer. In terms of adhesive properties, R ¹ is is a hydrogen atom and R ² is of C _4-8 It is preferable to use alkyl acrylate which is a chain alkyl group (hereinafter, simply referred to as C _4-8 alkyl acrylate) as a main monomer.

Specific examples of alkyl (meth)acrylates in which R ² is a C _1-20 chain alkyl group are not particularly limited, and examples thereof include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, and isopropyl. (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl(meth)acrylate, heptyl(meth)acrylate, 2-ethylhexyl(meth)acrylate, octyl(meth)acrylate, isooctyl(meth)acrylate, nonyl(meth)acrylate lyate, isononyl(meth)acrylate, decyl(meth)acrylate, isodecyl(meth)acrylate, undecyl(meth)acrylate, dodecyl(meth)acrylate, tridecyl(meth)acrylate, tetra Decyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, nonadecyl (meth)acrylate, eicosyl ( Meth) acrylate etc. are mentioned. These alkyl (meth)acrylates can be used individually by 1 type or in combination of 2 or more types. Preferable examples of alkyl (meth)acrylates include n-butyl acrylate (BA) and 2-ethylhexyl acrylate (2EHA).

The proportion of the alkyl (meth)acrylate in the monomer component constituting the acrylic polymer is typically more than 50% by weight, for example, 70% by weight or more, may be 85% by weight or more, or 90% by weight. You can do more than that. The upper limit of the proportion of alkyl (meth)acrylate is not particularly limited, but it is preferably 99.5% by weight or less (eg, 99% by weight or less), or properties based on secondary monomers such as carboxy group-containing monomers (eg, cohesive force) ) may be 98% by weight or less (for example, less than 97% by weight) from the viewpoint of favorably exhibiting. Alternatively, the acrylic polymer may be obtained by substantially polymerizing only alkyl (meth)acrylate.

In the case of using C _4-8 alkyl acrylate as the monomer component, the proportion of C _4-8 alkyl acrylate among the alkyl (meth) acrylates contained in the monomer component is preferably 70% by weight or more, and 90 It is more preferable that it is more than weight %.

A secondary monomer may be copolymerized in the acrylic polymer in the technique disclosed herein. As a secondary monomer capable of introducing a functional group that can be a crosslinking origin in an acrylic polymer or contributing to an improvement in adhesive strength, a carboxy group-containing monomer, a hydroxyl group (OH group)-containing monomer, an acid anhydride group-containing monomer, an amide group-containing monomer, Amino group-containing monomers, epoxy group-containing monomers, cyano group-containing monomers, keto group-containing monomers, monomers having a nitrogen atom-containing ring, alkoxysilyl group-containing monomers, and imide group-containing monomers. These secondary monomers can be used individually by 1 type or in combination of 2 or more types.

As one suitable example of the acrylic polymer in the technology disclosed herein, an acrylic polymer copolymerized with a carboxy group-containing monomer as the secondary monomer may be mentioned. Examples of the carboxy group-containing monomer include acrylic acid (AA), methacrylic acid (MAA), carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, isocrotonic acid, and the like. is exemplified Especially, AA and MAA are preferable.

Another preferred example is an acrylic polymer copolymerized with a hydroxyl group-containing monomer as the secondary monomer. Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, Hydroxyalkyl (meth)acrylates, such as 4-hydroxybutyl (meth)acrylate; polypropylene glycol mono(meth)acrylate; N-hydroxyethyl (meth)acrylamide etc. are mentioned. Among them, as a preferred hydroxyl group-containing monomer, hydroxyalkyl (meth)acrylates in which the alkyl group is linear with 2 to 4 carbon atoms are exemplified.

When the monomer component constituting the acrylic polymer contains the functional group-containing monomer described above, the content of the functional group-containing monomer in the monomer component is not particularly limited. From the viewpoint of appropriately exhibiting the effect of using the functional group-containing monomer, the content of the functional group-containing monomer in the monomer component can be, for example, 0.1% by weight or more, preferably 0.5% by weight or more, and 1% by weight or more. can be done with In addition, from the viewpoint of making it easy to balance the adhesive performance in relation to the main monomer, the content of the functional group-containing monomer in the monomer component is suitably 40% by weight or less, preferably 20% by weight or less, It is good also as 10 weight% or less (for example, 5 weight% or less).

In the base polymer according to some preferred embodiments, a monomer component constituting the base polymer (eg, an acrylic polymer) may include a carboxy group-containing monomer. When the monomer component contains a carboxy group-containing monomer, it becomes easier to obtain a pressure-sensitive adhesive sheet exhibiting good adhesive properties (cohesion, etc.). In addition, it may be advantageous to improve the adhesion between the pressure-sensitive adhesive layer and the adherend. Furthermore, by copolymerizing an appropriate amount of a carboxy group-containing monomer, even when a black colorant such as carbon black is blended into the adhesive, the colorant is easily dispersed in the layer and the adhesive properties can be favorably maintained.

In the aspect in which the carboxyl group-containing monomer is copolymerized with the base polymer, the content of the carboxy group-containing monomer in the monomer component constituting the base polymer is not particularly limited, and is, for example, 0.2% by weight or more of the monomer component (typically 0.5% by weight or more), preferably 1% by weight or more, 2% by weight or more, or 3% by weight or more. A higher effect is exhibited by making content of a carboxy group-containing monomer more than 3 weight%. In some embodiments, the content of the carboxy group-containing monomer may be 3.2% by weight or more, may be 3.5% by weight or more, may be 4% by weight or more, may be 4.5% by weight or more, can also The upper limit of the content of the carboxy group-containing monomer is not particularly limited, and may be, for example, 15% by weight or less, 12% by weight or less, or 10% by weight or less. The technology disclosed herein can be preferably carried out even in an embodiment in which the content of the carboxyl group-containing monomer is 7% by weight or less (typically less than 7% by weight, such as 6.8% by weight or less, or 6.0% by weight or less) of the monomer component. there is.

The monomer component constituting the acrylic polymer may contain other copolymerization components other than the above-mentioned secondary monomers for the purpose of improving cohesive force or the like. Examples of other copolymerization components include vinyl ester monomers such as vinyl acetate, vinyl propionate, and vinyl laurate; Aromatic vinyl compounds, such as styrene, substituted styrene ((alpha)-methylstyrene etc.), and vinyltoluene; cycloalkyl (meth)acrylates such as cyclohexyl (meth)acrylate, cyclopentyl (meth)acrylate, and isobornyl (meth)acrylate; Aryl(meth)acrylates (eg phenyl(meth)acrylate), aryloxyalkyl(meth)acrylates (eg phenoxyethyl(meth)acrylate), arylalkyl(meth)acrylates (eg benzyl(meth)acrylate) acrylate) and aromatic ring-containing (meth)acrylates; olefinic monomers such as ethylene, propylene, isoprene, butadiene, and isobutylene; chlorine-containing monomers such as vinyl chloride and vinylidene chloride; isocyanate group-containing monomers such as 2-(meth)acryloyloxyethyl isocyanate; alkoxy group-containing monomers such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate; vinyl ether monomers such as methyl vinyl ether and ethyl vinyl ether; 1,6-hexanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, etc., having two or more (eg, 3 or more) polymerizable functional groups (eg, (meth)acryloyl groups) in one molecule polyfunctional monomers; etc. can be mentioned.

The amount of such other copolymerization components may be appropriately selected depending on the purpose and use and is not particularly limited, but from the viewpoint of appropriately exhibiting the effect associated with use, it is appropriate to be 0.05% by weight or more, and even if it is set to 0.5% by weight or more do. In addition, from the viewpoint of making it easy to balance the adhesive performance, the content of the other copolymerization component in the monomer component is suitably 20% by weight or less, and 10% by weight or less (for example, 5% by weight or less). The technique disclosed herein can be preferably carried out even in an aspect in which the monomer component does not substantially contain other copolymerization components. Here, the fact that the monomer component does not substantially contain other copolymerization components means that other copolymerization components are not used at least intentionally, and other copolymerization components may be unintentionally included, for example, in an amount of 0.01% by weight or less. can

It is appropriate that the copolymerization composition of the acrylic polymer is designed such that the polymer has a glass transition temperature (Tg) of about -15°C or less (for example, about -70°C or more -15°C or less). Here, the Tg of the acrylic polymer refers to Tg obtained by Fox's formula based on the composition of the monomer component used in the synthesis of the polymer. As shown below, Fox's formula is a relational expression between the Tg of the copolymer and the glass transition temperature (Tgi) of a homopolymer obtained by homopolymerization of each of the monomers constituting the copolymer.

1/Tg = Σ (Wi/Tgi)

In addition, in Fox's formula, Tg is the glass transition temperature of the copolymer (unit: K), Wi is the weight fraction of monomer (i) in the copolymer (copolymerization ratio based on weight), and Tgi is the amount of monomer (i) It represents the glass transition temperature (unit: K) of the homopolymer.

As the glass transition temperature of the homopolymer used for calculating Tg, a known material, specifically, a numerical value described in "Polymer Handbook" (3rd edition, John Wiley & Sons, Inc., 1989) shall be used. For a monomer for which a plurality of types of values are described in this document, the highest value is adopted. When it is not described also in the said Polymer Handbook, the value obtained by the measuring method described in Unexamined-Japanese-Patent No. 2007-51271 shall be used.

Although not particularly limited, from the viewpoint of impact resistance and adhesion to adherends, the Tg of the acrylic polymer is advantageously about -25°C or less, preferably about -35°C or less, and more preferably about -40°C. below °C. In some embodiments, from the viewpoint of cohesive force, the Tg of the acrylic polymer may be, for example, about -70°C or higher, about -65°C or higher, about -60°C or higher, or about -55°C or higher. The technology disclosed herein can be preferably implemented in an aspect in which the Tg of the acrylic polymer is about -65°C or more -35°C or less (eg, about -55°C or more -40°C or less). The Tg of the acrylic polymer can be adjusted by appropriately changing the monomer composition (that is, the type and usage ratio of the monomers used in the synthesis of the polymer).

The method for obtaining the acrylic polymer is not particularly limited, and various polymerization methods known as methods for synthesizing acrylic polymers, such as solution polymerization, emulsion polymerization, bulk polymerization, suspension polymerization, and photopolymerization, can be appropriately employed. For example, a solution polymerization method can be preferably employed. The polymerization temperature when performing solution polymerization can be appropriately selected according to the types of monomers and solvents used, the type of polymerization initiator, etc. there is.

The solvent (polymerization solvent) used for solution polymerization can be appropriately selected from conventionally known organic solvents (toluene, ethyl acetate, etc.). The initiator used for polymerization can be appropriately selected from conventionally known polymerization initiators (for example, azo polymerization initiators such as 2,2'-azobisisobutyronitrile (AIBN), peroxide initiators, etc.) depending on the type of polymerization method. can The usage amount of the polymerization initiator may be a normal usage amount, and can be selected from, for example, a range of about 0.005 to 1 part by weight (typically about 0.01 to 1 part by weight) with respect to 100 parts by weight of the monomer component.

The weight average molecular weight (Mw) of the base polymer (preferably acrylic polymer) in the technique disclosed herein is not particularly limited, and may be, for example, in the range of about 10×10 ^{4 to} 500×10 ⁴ . From the viewpoint of adhesive performance, the Mw of the base polymer is about 30 × 10 ^{4 to} 200 × 10 ⁴ (more preferably about 45 × 10 ^{4 to} 150 × 10 ⁴ , typically about 65 × 10 ^{4 to} 130 × 10 ⁴ ) is preferred. By using a base polymer having a high Mw, better impact resistance tends to be easily obtained by utilizing the cohesive force of the polymer itself. Here, Mw means the value of standard polystyrene conversion obtained by GPC (gel permeation chromatography). As the GPC device, for example, model name "HLC-8320GPC" (column: TSKgelGMH-H(S), manufactured by Tosoh Corporation) can be used.

(coloring agent)

The pressure-sensitive adhesive layer disclosed herein typically contains a colorant. By using a colorant, a pressure-sensitive adhesive layer having a light transmittance of 20% or less and satisfying L ^* 20 or more and 70 or less specified in the L ^* a ^* b ^* color system can be preferably realized. The colorant may be, for example, a colorant such as black, gray, white, red, blue, yellow, green, yellow-green, orange, purple, gold, silver, or pearl. The colorant may be contained in the pressure-sensitive adhesive layer typically in a dispersed state (may be in a dissolved state) in the constituent materials of the pressure-sensitive adhesive layer. As a coloring agent, conventionally well-known pigments and dyes can be used. As a pigment, an inorganic pigment and an organic pigment are mentioned. The pressure-sensitive adhesive layer preferably contains at least two types of colorants (a first colorant and a second colorant).

(first colorant)

The colorant (also referred to as the first colorant) contained in the pressure-sensitive adhesive layer according to the preferred embodiment is not particularly limited, and, for example, a component capable of absorbing and attenuating light traveling through the pressure-sensitive adhesive layer is used. The first colorant may be a component that reduces the light transmittance of the pressure-sensitive adhesive layer (henceforth referred to as a 'light transmittance reducing component'). As such a 1st colorant, a black colorant can be used preferably from the point which can adjust light-shielding property efficiently with a small amount of colorant. Specific examples of black colorants include carbon black, graphite, aniline black, perylene black, cyanine black, titanium black, inorganic pigment hematite, activated carbon, molybudenum disulfide, chromium complexes, and anthraquinone colorants. A black colorant can be used individually by 1 type or in combination of 2 or more types suitably.

In some preferred embodiments, the pressure-sensitive adhesive layer contains carbon black particles as a colorant (first colorant). As the carbon black particles used, those generally referred to as carbon black (furnace black, channel black, acetylene black, thermal black, lamp black, smoke smoke, etc.) can be used without particular limitation. As the carbon black particles, it is also possible to use surface-modified carbon black particles having a functional group such as a carboxyl group, an amino group, a sulfonic acid group, or a silicon-containing group (for example, an alkoxysilyl group or an alkylsilyl group). Such surface-modified carbon black particles are also referred to as self-dispersing carbon black, and the addition of a dispersant becomes unnecessary or the addition amount thereof can be reduced. These carbon black particles can be used individually by 1 type or in combination of 2 or more types.

A particulate colorant (pigment) can be preferably used from the viewpoint that the light-shielding properties of the pressure-sensitive adhesive layer can be efficiently adjusted with a small amount of the colorant. In some preferred embodiments, a colorant (eg, a particulate black colorant such as carbon black) having an average particle diameter of about 10 nm or greater (eg, about 30 nm or greater) may be used. The average particle diameter may be, for example, about 50 nm or more, about 100 nm or more, or about 150 nm or more. The upper limit of the average particle diameter of the coloring agent is not particularly limited, and may be, for example, about 3000 nm or less, and about 1000 nm or less. From the viewpoint of improving light-shielding properties, the average particle diameter of the colorant is suitably about 500 nm or less, preferably about 300 nm or less, more preferably about 250 nm or less, still more preferably about 200 nm or less (for example, about 120 nm or less, and further about 100 nm or less).

In addition, the average particle diameter of the colorant in this specification refers to the volume average particle diameter, and specifically, at 50% of the integrated value in the particle size distribution measured based on the laser scattering/diffraction method based particle size distribution analyzer. It indicates the particle diameter (50% volume average particle diameter; hereinafter sometimes abbreviated as D ₅₀ ). As the measuring device, for example, "Microtrac MT3000II" manufactured by Microtrac Bell Co., Ltd., product name, or an equivalent product thereof can be used.

In the technique disclosed herein, the form of addition of the colorant (preferably black colorant such as carbon black particles) to the pressure-sensitive adhesive composition is not particularly limited. A colorant such as carbon black particles may be added to the pressure-sensitive adhesive composition in the form of a dispersion in which the particles are dispersed in a dispersion medium. The dispersion medium constituting the dispersion is not particularly limited, and water (ion-exchanged water, reverse osmosis water, distilled water, etc.) or various organic solvents (alcohols such as ethanol; ketones such as acetone; butyl cellosolve, propylene glycol monomethyl ethers such as ether acetate; esters such as ethyl acetate; aromatic hydrocarbons such as toluene; mixed solvents thereof); and aqueous mixed solvents of water and the above organic solvents. The dispersion liquid may contain the dispersing agent described above. By mixing the dispersion into the pressure-sensitive adhesive composition, the pressure-sensitive adhesive composition contains a colorant (preferably a black colorant such as carbon black particles) and may also contain a dispersant.

The content of the first colorant (preferably black colorant such as carbon black particles) is appropriately set in consideration of adherend hiding properties, required adhesive properties, and the like, and is not limited to a specific range. In addition, the content of the first colorant may also differ depending on the type of adhesive, the shape or particle diameter of the first colorant, compatibility with the adhesive, and the like. The content of the first colorant in the pressure-sensitive adhesive layer is suitably about 0.01% by weight or more, may be 0.05% by weight or more, may be 0.08% by weight or more, and from the viewpoint of the adherend hiding property, preferably about 0.1% by weight or more ( Specifically, 0.10% by weight or more), more preferably about 0.2% by weight or more, and may be about 0.3% by weight or more. In addition, the content of the first colorant (preferably black colorant such as carbon black particles) can be about 10% by weight or less, preferably about 3% by weight or less, and the light transmittance of a predetermined value or less and a predetermined range From the viewpoint of achieving both L ^* of , it is preferably about 2% by weight or less (typically less than 2% by weight), more preferably about 1% by weight or less, still more preferably about 0.6% by weight or less, and about It may be 0.5% by weight or less (eg, 0.4% by weight or less). In some embodiments, the content of the first colorant (preferably black colorant such as carbon black particles) may be 0.25% by weight or less, or 0.15% by weight or less. In the aspect in which the content of the first colorant is limited, the effect of suppressing the concealment non-uniformity by setting the color tone to be the same as that of the adherend is easily exhibited. In addition, by limiting the content of the first colorant, adhesive properties such as adhesive strength tend to be easily maintained.

(Second colorant)

In an aspect in which the pressure-sensitive adhesive layer includes at least two kinds of colorants, the second colorant used in addition to the first colorant described above is not particularly limited, and for example, a component that adjusts L ^* of the pressure-sensitive adhesive layer (therefore, a 'brightness adjusting component '.) is used. Such second colorants may be selected from, for example, white colorants or gray colorants. The second colorant may be one or two or more selected from inorganic materials (eg, metals and metal compounds), organic materials, and organic-inorganic composites. Specific examples of the second colorant include titanium oxide (titanium dioxide such as rutile-type titanium dioxide and anatase-type titanium dioxide), zinc oxide, cerium oxide, aluminum oxide, silicon oxide, zirconium oxide, magnesium oxide, calcium oxide, tin oxide, and oxide. Metal oxides, such as barium, cesium oxide, and yttrium oxide; Carbonic acid compounds, such as magnesium carbonate, calcium carbonate (light calcium carbonate, heavy calcium carbonate, etc.), barium carbonate, and zinc carbonate; hydroxides such as aluminum hydroxide, calcium hydroxide, magnesium hydroxide, and zinc hydroxide; silicic acid compounds such as aluminum silicate, magnesium silicate, and calcium silicate; barium sulfate, calcium sulfate, barium stearate, zinc oxide, zinc sulfide, talc, clay, kaolin, titanium phosphate, mica, gypsum, white carbon, diatomaceous earth, bentonite, lithopone, zeolite, sericite, hydrous halloysite and the like; and inorganic materials such as acrylic resins, polystyrene-based resins, polyurethane-based resins, amide-based resins, polycarbonate-based resins, silicone-based resins, urea-formalin-based resins, and organic materials such as melamine-based resins. Further, the second colorant may be defined as a colorant that does not include the carbon black particles and is different from the carbon black particles. Typically, the light absorbing black colorant is not contained in the second colorant.

In some preferred aspects, the pressure-sensitive adhesive layer contains a metal oxide as the second colorant. By using the first colorant (preferably black colorant) and the metal oxide in combination, the light transmittance of a predetermined value or less and L ^* within a predetermined range can be favorably compatible. As the metal oxide, one capable of realizing a desired L ^* can be selected from the materials described above. Suitable examples include titanium oxide, zinc oxide, cerium oxide, aluminum oxide, silicon oxide, zirconium oxide, magnesium oxide, and calcium oxide. Among these, titanium oxide, silicon oxide, and zirconium oxide are preferred, and titanium oxide is particularly preferred. desirable. A metal oxide can be used individually by 1 type or in combination of 2 or more types.

In the aspect in which the second colorant has a particle shape, the average particle diameter of the second colorant (for example, a white colorant, preferably metal oxide particles) is not particularly limited. Depending on the thickness of the pressure-sensitive adhesive layer, the type of pressure-sensitive adhesive, etc., particles of an appropriate size capable of realizing a desired L ^* can be used. The average particle diameter of the second colorant can be, for example, about 1 nm or more, and preferably about 5 nm or more. From the viewpoint of the effect of containing the second colorant (e.g., control of L ^* ), compatibility, handleability, etc., the average particle diameter of the second colorant may preferably be about 10 nm or more or about 20 nm or more, and about 30 nm or more may be sufficient. The upper limit of the average particle diameter is preferably about 300 nm or less, for example, from the viewpoint of maintaining adhesive properties, etc., and from the viewpoint of the effect of containing the second colorant (eg, control of L ^* ), etc., it is preferably less than 100 nm ( For example, 90 nm or less), more preferably about 70 nm or less, still more preferably about 50 nm or less, or about 35 nm or less (eg about 25 nm or less).

The content of the second colorant (eg, white colorant, preferably a metal oxide) in the pressure-sensitive adhesive layer is appropriately set in consideration of the effect of containing the second colorant (eg, control of L ^* ), required adhesive properties, and the like, and is specified. not limited to the scope In addition, the content of the second colorant may also differ depending on the type of adhesive, the shape or particle diameter of the second colorant, compatibility with the adhesive, and the like. The content of the second colorant in the pressure-sensitive adhesive layer is appropriately about 1% by weight or more, preferably about 2% by weight or more, more preferably from the viewpoint of effectively obtaining the effect of containing the second colorant (e.g., L ^* control). It is preferably about 3% by weight or more, about 4% by weight or more, or about 5% by weight or more. The content of the second colorant in the pressure-sensitive adhesive layer may be about 20% by weight or less (for example, less than 20% by weight) from the viewpoint of compatibility with the pressure-sensitive adhesive component and maintenance of adhesive properties such as adhesive strength and impact resistance. It may be about 15% by weight or less, preferably about 10% by weight or less, preferably about 8% by weight or less, more preferably about 6% by weight or less, and may be about 5% by weight or less.

In the aspect in which the pressure-sensitive adhesive layer contains at least two types of colorants, the ratio between the amount (C1) of the first colorant and the amount (C2) of the second colorant is not particularly limited. From the viewpoint of achieving both the desired light transmittance and L ^* in a predetermined range, in some preferred embodiments, the amount (C1) of the first colorant (preferably black colorant) and the second colorant (eg white colorant, suitably The weight ratio (C1/C2) of the amount (C2) of the silver metal oxide) is 0.001 or more (for example, 0.005 or more), suitably 0.01 or more, preferably 0.02 or more, may be 0.05 or more, may be 0.08 or more, may be 0.10 It may be more than (for example, 0.12 or more). The larger the weight ratio (C1/C2), the more preferably the effect of adding the first colorant is exhibited. In an aspect in which the first colorant is a black colorant, the adherend hiding property tends to be improved. In some embodiments, the weight ratio (C1/C2) may be 0.50 or less, 0.40 or less (eg 0.35 or less), preferably 0.30 or less, 0.20 or less, 0.15 or less, or 0.12 or less. and may be 0.09 or less. In some other embodiments, the weight ratio (C1/C2) may be 0.05 or less (eg, 0.03 or less). The smaller the weight ratio (C1/C2), the more the effect of adding the second colorant (eg, control of L ^* ) is preferably exhibited.

In an aspect in which the pressure-sensitive adhesive layer includes a black colorant as the first colorant and a metal oxide as the second colorant, the content of the black colorant and colorants other than the metal oxide is not particularly limited, and can be, for example, less than 30% by weight. , Less than 10% by weight is preferable, for example, less than 5.0% by weight may be sufficient, and less than 3.0% by weight (eg, less than 2.0% by weight, furthermore less than 1% by weight) can be made. The technique disclosed herein can be implemented in an aspect provided with a pressure-sensitive adhesive layer that does not substantially contain a black colorant and a colorant other than a metal oxide. In addition, in the present specification, 'substantially not included' means not intentionally added, and for example, the content in the pressure-sensitive adhesive layer is 0.3% by weight or less (eg, 0.1% by weight or less, typically 0.01% by weight or less). can

In addition, as a colorant, what surface-treated the material (particulate colorant) illustrated as the above-mentioned colorant from a viewpoint of compatibility with an adhesive component can be used by the surface treatment agent. As the surface treatment, since an appropriate treatment can be selected according to the type of core particles, the type of dispersion medium, etc., it is not limited to a specific treatment.

The pressure-sensitive adhesive composition disclosed herein may contain a component that contributes to improving the dispersibility of the colorant. Such a dispersibility enhancing component may be, for example, a polymer, an oligomer, a liquid resin, or a surfactant (anionic, cationic, nonionic, or amphoteric surfactant). The dispersibility improving component can be used individually by 1 type or in combination of 2 or more types. It is preferable that the dispersibility improving component is dissolved in the pressure-sensitive adhesive composition. The oligomer is, for example, a low molecular weight polymer of monomer components including one or two or more of the acrylic monomers as exemplified above (eg, Mw is less than about 10×10 ⁴ , preferably less than 5×10 ^{4 )} . acrylic oligomer). The liquid resin is, for example, a tackifying resin having a softening point of about 50° C. or less, more preferably about 40° C. or less (typically rosin-based, terpene-based, hydrocarbon-based tackifying resins such as hydrogenated rosin methyl ester, etc.) can be With such a dispersibility improving component, it is possible to suppress non-uniform dispersion of the coloring agent (for example, particulate black colorant such as carbon black), and consequently to suppress non-uniform color of the pressure-sensitive adhesive layer. Therefore, it is possible to form a pressure-sensitive adhesive layer with better appearance quality.

The form of addition of the dispersibility improving component is not particularly limited, and may be included in a solution containing a colorant (for example, a black colorant such as carbon black particles) before blending into the pressure-sensitive adhesive composition, or at the same timing as the colorant in the pressure-sensitive adhesive composition, or You may supply before and after addition.

The content of the dispersibility improving component is not particularly limited, and is about 20% by weight or less (preferably about 10% by weight or less, more preferably about 10% by weight or less, more preferably about 10% by weight or less) of the entire pressure-sensitive adhesive layer from the viewpoint of suppressing the influence on the adhesive properties (eg, decrease in cohesiveness). Preferably, it is 7% by weight or less, such as about 5% by weight or less). In some embodiments, the content of the dispersibility enhancing component may be about 10 times or less (preferably about 5 times or less, such as about 3 times or less) the weight of the colorant. On the other hand, from the viewpoint of suitably exhibiting the effect of the dispersibility improving component, the content thereof is about 0.2% by weight or more (typically about 0.5% by weight or more, preferably about 1% by weight or more) of the entire pressure-sensitive adhesive layer. it is suitable In some embodiments, the content of the dispersibility enhancing component can be about 0.2 times or more (preferably about 0.5 times or more, such as 1 time or more) the weight of the colorant.

The content (total amount, total content) of the colorant in the pressure-sensitive adhesive layer is appropriately set in consideration of both the target light transmittance and L ^* and the required adhesive properties, etc., and is not limited to a specific range. The total amount of the colorant in the pressure-sensitive adhesive layer is suitably about 1% by weight or more, preferably about 2% by weight or more, more preferably about 3% by weight or more, may be about 3.2% by weight or more, or about 3.5% by weight. It may be more than 4% by weight or more. The total amount of the colorant in the pressure-sensitive adhesive layer may be about 30% by weight or less, usually about 20% by weight or less (from the viewpoint of compatibility with the pressure-sensitive adhesive component and maintenance of adhesive properties such as adhesive strength and impact resistance) For example, less than 20% by weight), may be about 15% by weight or less, preferably about 10% by weight or less, preferably about 8% by weight or less, more preferably about 6% by weight or less, and about 5% by weight or less may be continued

(tackifying resin)

The pressure-sensitive adhesive layer in the technique disclosed herein may contain a tackifying resin. In this way, the peeling strength of the pressure-sensitive adhesive sheet can be increased. As the tackifying resin, phenol-based tackifying resin, terpene-based tackifying resin, modified terpene-based tackifying resin, rosin-based tackifying resin, hydrocarbon-based tackifying resin, epoxy-based tackifying resin, polyamide-based tackifying resin, elastomer One type or two or more types selected from various known tackifying resins such as type tackifying resins and ketone type tackifying resins can be used. Among them, phenol-based tackifying resins, terpene-based tackifying resins, and modified terpene-based tackifying resins are preferred, and phenol-based tackifying resins (preferably terpene phenol resins) are more preferred.

Examples of phenolic tackifying resins include terpene phenol resins, hydrogenated terpene phenol resins, alkyl phenol resins, and rosin phenol resins.

Terpene phenol resin refers to a polymer containing a terpene residue and a phenol residue, and includes a copolymer of terpenes and phenol compounds (terpene-phenol copolymer resin) and a phenol-modified terpene homopolymer or copolymer ( It is a concept including both phenol-modified terpene resins). Preferred examples of terpenes constituting such a terpene phenol resin include monoterpenes such as α-pinene, β-pinene, and limonene (including d-, l- and d/l-forms (dipentene)). can The hydrogenated terpene phenol resin refers to a hydrogenated terpene phenol resin having a structure obtained by hydrogenating such a terpene phenol resin. It is sometimes called hydrogenated terpene phenol resin.

Alkyl phenol resin is a resin (oil-based phenol resin) obtained from an alkyl phenol and formaldehyde. Examples of the alkylphenol resin include novolak type and resol type resins.

The rosin phenol resin is typically a phenol-modified product of rosin or various rosin derivatives described above (including rosin esters, unsaturated fatty acid-modified rosin, and unsaturated fatty acid-modified rosin esters). Examples of the rosin phenol resin include rosin phenol resins obtained by a method of thermal polymerization by adding phenol to rosin or various rosin derivatives described above using an acid catalyst.

Examples of the terpene-based tackifying resin include polymers of terpenes (typically monoterpenes) such as α-pinene, β-pinene, d-limonene, l-limonene, and dipentene. It may be a homopolymer of one type of terpenes or a copolymer of two or more types of terpenes. Examples of homopolymers of one type of terpenes include α-pinene polymers, β-pinene polymers, and dipentene polymers. As an example of a modified terpene resin, what modified|denatured the said terpene resin is mentioned. Specifically, styrene-modified terpene resins and hydrogenated terpene resins are exemplified.

The softening point of the tackifying resin is not particularly limited. From the viewpoint of improving cohesive force, in some embodiments, a tackifying resin having a softening point (softening temperature) of about 80°C or higher (preferably about 100°C or higher, such as greater than 105°C) can be preferably employed. In the technology disclosed herein, the total amount of the tackifying resin contained in the pressure-sensitive adhesive layer is 100% by weight, of which more than 50% by weight (more preferably more than 70% by weight, for example, more than 90% by weight) has the softening point. It can be preferably carried out in an aspect of a tackifying resin having. For example, a phenolic tackifying resin (such as terpene phenol resin) having such a softening point can be preferably used. The tackifying resin may contain, for example, a terpene phenol resin having a softening point of about 135°C or higher (moreover, 140°C or higher). The upper limit of the softening point of the tackifying resin is not particularly limited. From the viewpoint of improving adhesion to adherends, in some embodiments, a tackifying resin having a softening point of about 200°C or less (more preferably about 150°C or less, such as less than 130°C) can be preferably used. In addition, the softening point of the tackifying resin can be measured based on the softening point test method (ring and ball method) specified in JIS K2207.

As some preferable aspect, the aspect in which the said tackifying resin contains 1 type, or 2 or more types of phenolic tackifying resin (typically terpene phenol resin) is mentioned. The technique disclosed herein is preferably carried out in an aspect, for example, in which the total amount of the tackifying resin is 100% by weight, of which about 25% by weight or more (more preferably about 30% by weight or more) is a terpene phenol resin. can About 50% by weight or more of the total amount of the tackifying resin may be a terpene phenol resin, and about 80% by weight or more (for example, about 90% by weight or more) may be a terpene phenol resin. Substantially all of the tackifying resin (for example, about 95 to 100% by weight, furthermore about 99 to 100% by weight) may be a terpene phenol resin.

Although not particularly limited, in some embodiments, the tackifying resin may include a tackifying resin having a hydroxyl value higher than 20 mgKOH/g. Especially, the tackifying resin whose hydroxyl value is 30 mgKOH/g or more is preferable. Hereinafter, a tackifying resin having a hydroxyl value of 30 mgKOH/g or more may be referred to as "high hydroxyl value resin". According to the tackifying resin in which such a high acid group contains a resin, a pressure-sensitive adhesive layer having excellent adhesion to an adherend and high cohesive force can be realized. In some aspect, the said tackifying resin may contain resin with a high hydroxyl value whose hydroxyl value is 50 mgKOH/g or more (more preferably 70 mgKOH/g or more).

In addition, as a value of the said hydroxyl value, the value measured by the potentiometric titration method prescribed|regulated by JISK0070:1992 is employable.

As the resin with a high hydroxyl value, one having a hydroxyl value of a predetermined value or more among the various tackifying resins described above can be used. High acid value resin can be used individually by 1 type or in combination of 2 or more types. For example, as a resin with a high hydroxyl value, a phenolic tackifying resin having a hydroxyl value of 30 mgKOH/g or more can be preferably employed. In some preferred aspects, as the tackifying resin, a terpene phenol resin having at least a hydroxyl value of 30 mgKOH/g or more is used. The terpene phenol resin is suitable because the hydroxyl value can be arbitrarily controlled according to the copolymerization ratio of phenol.

The upper limit of the hydroxyl value of the resin having a high hydroxyl value is not particularly limited. From the viewpoint of compatibility with the base polymer, etc., the hydroxyl value of the resin having a high hydroxyl value is suitably about 200 mgKOH/g or less, preferably about 180 mgKOH/g or less, and more preferably about 160 mgKOH. /g or less, more preferably about 140 mgKOH/g or less. The technology disclosed herein may be preferably carried out in an aspect in which the tackifying resin includes a resin having a high hydroxyl value of 30 to 160 mgKOH/g (eg, a phenolic tackifying resin, preferably a terpene phenol resin) there is. In some embodiments, a resin having a high hydroxyl value of 30 to 80 mgKOH/g (eg 30 to 65 mgKOH/g) may be preferably employed. In some other embodiments, a resin having a high hydroxyl value of 70 to 140 mgKOH/g can be preferably employed.

Although not particularly limited, when a resin with a high acid group is used, the ratio of the resin with a high acid group (for example, terpene phenol resin) to the total tackifying resin included in the pressure-sensitive adhesive layer may be, for example, about 25% by weight or more , about 30% by weight or more is preferred, and about 50% by weight or more (eg, about 80% by weight or more, typically about 90% by weight or more) is more preferred. Substantially all of the tackifying resin (for example, about 95 to 100% by weight, furthermore about 99 to 100% by weight) may be a resin with a high acid group.

In the case where the pressure-sensitive adhesive layer contains a tackifying resin, the amount of the tackifying resin used is not particularly limited, and can be appropriately set in the range of about 1 to 100 parts by weight, for example, based on 100 parts by weight of the base polymer. From the viewpoint of suitably exhibiting the effect of improving the peel strength, the amount of the tackifying resin based on 100 parts by weight of the base polymer (eg acrylic polymer) is suitably set to 5 parts by weight or more, and preferably set to 10 parts by weight or more. It is preferable and it is good also as 15 parts weight or more. In addition, from the viewpoint of impact resistance and cohesion, the amount of the tackifying resin relative to 100 parts by weight of the base polymer (eg acrylic polymer) is suitably 50 parts by weight or less, and may be 40 parts by weight or less, and 30 parts by weight or less.

(crosslinking agent)

In the technique disclosed herein, the pressure-sensitive adhesive composition used for forming the pressure-sensitive adhesive layer may contain a crosslinking agent as needed. The type of crosslinking agent is not particularly limited, and can be appropriately selected and used from conventionally known crosslinking agents. Examples of such crosslinking agents include isocyanate crosslinking agents, epoxy crosslinking agents, oxazoline crosslinking agents, aziridine crosslinking agents, melamine crosslinking agents, peroxide crosslinking agents, urea crosslinking agents, metal alkoxide crosslinking agents, metal chelate crosslinking agents, and metal salt crosslinking agents. , carbodiimide-based crosslinking agents, hydrazine-based crosslinking agents, amine-based crosslinking agents, silane coupling agents, and the like. Among them, isocyanate-based crosslinking agents, epoxy-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, and melamine-based crosslinking agents are preferred, isocyanate-based crosslinking agents and epoxy-based crosslinking agents are more preferred, and isocyanate-based crosslinking agents are particularly preferred. The use of an isocyanate-based crosslinking agent tends to provide better impact resistance than other crosslinking systems while obtaining cohesive force of the pressure-sensitive adhesive layer. In addition, the use of an isocyanate-based crosslinking agent is advantageous in terms of improving adhesion to adherends made of polyester resin, such as PET. A crosslinking agent can be used individually by 1 type or in combination of 2 or more types.

As the isocyanate-based crosslinking agent, polyfunctional isocyanates (referring to compounds having an average of two or more isocyanate groups per molecule, including those having an isocyanurate structure) can be preferably used. An isocyanate-type crosslinking agent can be used individually by 1 type or in combination of 2 or more types.

Examples of polyfunctional isocyanates include aliphatic polyisocyanates, alicyclic polyisocyanates, and aromatic polyisocyanates.

Specific examples of aliphatic polyisocyanates include 1,2-ethylene diisocyanate; tetramethylene diisocyanates such as 1,2-tetramethylene diisocyanate, 1,3-tetramethylene diisocyanate, and 1,4-tetramethylene diisocyanate; 1,2-hexamethylene diisocyanate, 1,3-hexamethylene diisocyanate, 1,4-hexamethylene diisocyanate, 1,5-hexamethylene diisocyanate, 1,6-hexamethylene diisocyanate, 2,5-hexamethylene diisocyanate hexamethylene diisocyanate such as isocyanate; 2-methyl-1,5-pentane diisocyanate, 3-methyl-1,5-pentane diisocyanate, and lysine diisocyanate.

Specific examples of alicyclic polyisocyanates include isophorone diisocyanate; cyclohexyl diisocyanates such as 1,2-cyclohexyl diisocyanate, 1,3-cyclohexyl diisocyanate, and 1,4-cyclohexyl diisocyanate; cyclopentyl diisocyanates such as 1,2-cyclopentyl diisocyanate and 1,3-cyclopentyl diisocyanate; Hydrogenated xylylene diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated tetramethylxylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, etc. are mentioned.

As specific examples of aromatic polyisocyanates, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 2,2' -Diphenylmethane diisocyanate, 4,4'-diphenyl ether diisocyanate, 2-nitrodiphenyl-4,4'-diisocyanate, 2,2'-diphenylpropane-4,4'-diisocyanate, 3 ,3'-dimethyldiphenylmethane-4,4'-diisocyanate, 4,4'-diphenylpropane diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, naphthylene-1,4-diisocyanate, Naphthylene-1,5-diisocyanate, 3,3'-dimethoxydiphenyl-4,4'-diisocyanate, xylylene-1,4-diisocyanate, xylylene-1,3-diisocyanate, etc. can be heard

As a preferred polyfunctional isocyanate, a polyfunctional isocyanate having an average of 3 or more isocyanate groups per molecule is exemplified. Such a trifunctional or higher functional isocyanate is a multimer (typically a dimer or a trimer), a derivative (e.g., an addition reaction product of a polyhydric alcohol and two or more polyfunctional isocyanates), a polymer, etc. can For example, dimer or trimer of diphenylmethane diisocyanate, isocyanurate compound of hexamethylene diisocyanate (trimeric adduct of isocyanurate structure), reaction product of trimethylolpropane and tolylene diisocyanate, trimethylol and polyfunctional isocyanates such as reaction products of propane and hexamethylene diisocyanate, polymethylene polyphenyl isocyanate, polyether polyisocyanate, and polyester polyisocyanate. Commercially available products of such polyfunctional isocyanates include "Duranate TPA-100" manufactured by Asahi Kasei Chemicals Co., Ltd., "Coronate L" manufactured by Tosoh Corporation, "Coronate HL", "Coronate HK", Copper "Coronate HX", copper "Coronate 2096", etc. are mentioned.

The usage amount of the isocyanate-based crosslinking agent is not particularly limited. For example, it can be about 0.5 parts by weight or more with respect to 100 parts by weight of the base polymer. From the viewpoint of coexistence of cohesion and adhesiveness, impact resistance, etc., the amount of isocyanate-based crosslinking agent used per 100 parts by weight of the base polymer can be, for example, 1.0 parts by weight or more, and 1.5 parts by weight or more (typically 2.0 parts by weight or more). , For example, 2.5 parts by weight or more). On the other hand, from the viewpoint of improving adhesion to the adherend, the amount of the isocyanate-based crosslinking agent used is suitably 10 parts by weight or less, 8 parts by weight or less, or 5 parts by weight or less with respect to 100 parts by weight of the base polymer. (For example, 3 parts by weight or less).

In some preferable aspects, as a crosslinking agent, an isocyanate crosslinking agent and at least one crosslinking agent having a different type of crosslinkable functional group from the isocyanate crosslinking agent are used in combination. According to the technology disclosed herein, a crosslinking agent other than an isocyanate-based crosslinking agent (that is, a crosslinking agent having a different type of crosslinkable reactive group from an isocyanate-based crosslinking agent. Hereinafter referred to as a 'non-isocyanate-based crosslinking agent') and an isocyanate-based crosslinking agent are used in combination. By doing so, excellent cohesive force can be exhibited. In addition, the pressure-sensitive adhesive layer in the technique disclosed herein may contain the crosslinking agent in a form after crosslinking reaction, before crosslinking reaction, in a form partially crosslinked, or in an intermediate or complex form thereof. The crosslinking agent is typically contained in the pressure-sensitive adhesive layer only in the form after the crosslinking reaction.

The type of non-isocyanate-based cross-linking agent that can be used in combination with the isocyanate-based cross-linking agent is not particularly limited, and can be appropriately selected and used from the above-mentioned cross-linking agents. A non-isocyanate type crosslinking agent can be used individually by 1 type or in combination of 2 or more types.

In some preferred embodiments, an epoxy-based crosslinking agent can be employed as the non-isocyanate-based crosslinking agent. For example, by using an isocyanate-based crosslinking agent and an epoxy-based crosslinking agent in combination, it is easy to achieve both cohesion and impact resistance. As the epoxy-based crosslinking agent, a compound having two or more epoxy groups in one molecule can be used without particular limitation. An epoxy-based crosslinking agent having 3 to 5 epoxy groups per molecule is preferable. An epoxy-type crosslinking agent can be used individually by 1 type or in combination of 2 or more types.

Although not particularly limited, specific examples of the epoxy-based crosslinking agent include, for example, N,N,N',N'-tetraglycidyl-m-xylenediamine, 1,3-bis(N,N-diglycidylamino methyl) cyclohexane, 1,6-hexanediol diglycidyl ether, polyethylene glycol diglycidyl ether, polyglycerol polyglycidyl ether, and the like. Examples of commercially available epoxy crosslinking agents include "TETRAD-C" and "TETRAD-X" manufactured by Mitsubishi Gas Chemical Co., Ltd., "Epicron CR-5L" manufactured by DIC, and "TETRAD-X" manufactured by Nagase ChemteX Co., Ltd. Denacol EX-512', trade name 'TEPIC-G' manufactured by Nissan Chemical Industries, Ltd., and the like.

The amount of the epoxy-based crosslinking agent used is not particularly limited. The amount of the epoxy-based crosslinking agent can be, for example, greater than 0 part by weight and less than or equal to about 1 part by weight (typically about 0.001 to 0.5 part by weight) with respect to 100 parts by weight of the base polymer. From the viewpoint of suitably exhibiting the effect of improving the cohesive force, the amount of the epoxy-based crosslinking agent is suitably about 0.002 parts by weight or more, preferably about 0.005 parts by weight or more, and about 0.008 parts by weight with respect to 100 parts by weight of the base polymer. The above is more preferable. In addition, from the viewpoint of improving adhesion to the adherend, the amount of the epoxy-based crosslinking agent is suitably about 0.2 parts by weight or less, preferably about 0.1 parts by weight or less, and about 0.05 parts by weight based on 100 parts by weight of the base polymer. Less than a part by weight is more preferred, and less than about 0.03 parts by weight (eg, about 0.025 parts by weight or less) is even more preferred. By reducing the amount of the epoxy-based crosslinking agent used, the impact resistance also tends to be improved.

In the technique disclosed herein, the relationship between the content of the isocyanate-based crosslinking agent and the content of the non-isocyanate-based crosslinking agent (eg, epoxy-based crosslinking agent) is not particularly limited. The content of the non-isocyanate-based crosslinking agent can be, for example, about 1/50 or less of the content of the isocyanate-based crosslinking agent. From the viewpoint of more appropriately achieving both adhesion and cohesion to the adherend, the content of the non-isocyanate-based crosslinking agent is suitably about 1/75 or less, and about 1/100 or less of the content of the isocyanate-based crosslinking agent on a weight basis. (for example, 1/150 or less). In addition, from the viewpoint of suitably exhibiting the effect of using an isocyanate-based crosslinking agent and a non-isocyanate-based crosslinking agent (e.g., an epoxy-based crosslinking agent) in combination, the content of the non-isocyanate-based crosslinking agent is about 1/1000 or more of the content of the isocyanate-based crosslinking agent. , for example, it is appropriate to set it to about 1/500 or more.

The total usage (total amount) of the crosslinking agent is not particularly limited. For example, it may be about 10 parts by weight or less based on 100 parts by weight of the base polymer (preferably acrylic polymer), preferably about 0.005 to 10 parts by weight, more preferably about 0.01 to 5 parts by weight. there is.

(rust inhibitor)

The pressure-sensitive adhesive layer according to some preferred embodiments may contain a rust inhibitor. The rust inhibitor is not particularly limited, and azole-based rust inhibitors, amine compounds, nitrites, ammonium benzoate, ammonium phthalate, ammonium stearate, ammonium palmitate, ammonium oleate, ammonium carbonate, dicyclohexylamine benzoate, urea, urotropin , thiourea, phenyl carbamate, cyclohexylammonium-N-cyclohexylcarbamate (CHC), and the like. Rust inhibitors can be used individually by 1 type or in combination of 2 or more types.

As the rust inhibitor, an azole-based rust inhibitor can be preferably used. As the azole-based rust inhibitor, a 5-membered ring aromatic compound containing two or more hetero atoms, wherein at least one of the hetero atoms is a nitrogen atom, an azole-based compound containing as an active ingredient can be preferably used. A suitable example of a compound that can be used as an azole-based rust preventive is a benzotriazole-based rust preventive containing a benzotriazole-based compound as an active ingredient. Suitable examples of the benzotriazole-based compound include 1,2,3-benzotriazole, 5-methylbenzotriazole, 4-methylbenzotriazole, and carboxybenzotriazole.

The content of the rust inhibitor is not particularly limited, and may be, for example, 0.01 part by weight or more (typically 0.05 part by weight or more) with respect to 100 parts by weight of the base polymer. From the viewpoint of obtaining a better effect of preventing metal corrosion, the content may be 0.1 part by weight or more, 0.3 part by weight or more, or 0.5 part by weight or more. On the other hand, from the viewpoint of increasing the cohesive force of the adhesive, the content of the rust inhibitor is suitably less than 8 parts by weight, 5 parts by weight or less, or 2 parts by weight or less with respect to 100 parts by weight of the base polymer.

(other additives)

The pressure-sensitive adhesive composition may contain, if necessary, various additives common in the field of pressure-sensitive adhesives such as leveling agents, crosslinking aids, plasticizers, softeners, antistatic agents, anti-aging agents, ultraviolet absorbers, antioxidants, and light stabilizers. Regarding these various additives, conventionally known ones can be used by conventional methods, and since they do not characterize the present invention in particular, detailed descriptions thereof are omitted.

(Adhesive composition)

The pressure-sensitive adhesive layer (layer containing an adhesive) disclosed herein is formed of a water-based pressure-sensitive adhesive composition, a solvent-type pressure-sensitive adhesive composition, a hot-melt-type pressure-sensitive adhesive composition, or an active energy ray-curable pressure-sensitive adhesive composition that is cured by irradiation of active energy rays such as ultraviolet rays or electron beams. It may be an adhesive layer. The water-based pressure-sensitive adhesive composition refers to a pressure-sensitive adhesive composition containing an pressure-sensitive adhesive (a pressure-sensitive adhesive layer forming component) in a solvent containing water as a main component (aqueous solvent), and typically, a water-dispersible pressure-sensitive adhesive composition (at least a part of the pressure-sensitive adhesive is dispersed in water Composition in the form) and the like are included. In addition, a solvent type adhesive composition refers to the adhesive composition of the form containing an adhesive in an organic solvent. As the organic solvent contained in the solvent-based pressure-sensitive adhesive composition, one or two or more of those exemplified as organic solvents (toluene, ethyl acetate, etc.) that can be used in the above solution polymerization can be used without particular limitation. The technique disclosed here can be preferably implemented in an aspect provided with a pressure-sensitive adhesive layer formed of a solvent-type pressure-sensitive adhesive composition from the viewpoint of adhesive properties and the like. In an aspect provided with a solvent-type pressure-sensitive adhesive layer formed from a solvent-type pressure-sensitive adhesive composition, the effect of the technique disclosed herein is preferably realized.

From the above, according to the present specification, a pressure-sensitive adhesive composition containing one or two or more types of components that may be included in the pressure-sensitive adhesive layer disclosed herein is provided. By using this pressure-sensitive adhesive composition, a pressure-sensitive adhesive layer having a light transmittance of 20% or less and L ^* of 20 or more and 70 or less can be formed. In some preferred aspects, the pressure-sensitive adhesive composition contains at least two kinds of colorants. In addition, a component (typically a base polymer) that can be included in the above-described pressure-sensitive adhesive layer may be included. The content (% by weight) of each component that can be included in the pressure-sensitive adhesive layer can be rephrased as the content (% by weight) on a solid content basis (also referred to as a non-volatile content basis) in the pressure-sensitive adhesive composition. Since the details of other adhesive compositions are as described in the adhesive layer, repetitive explanations are omitted.

(formation of adhesive layer)

The pressure-sensitive adhesive layer disclosed herein can be formed by a conventionally known method. For example, a method of forming an adhesive layer by applying an adhesive composition to a surface having peelability (release surface) and drying it can be employed. In the PSA sheet having a configuration including a supporting substrate, for example, a method (direct method) of directly applying (typically applying) an adhesive composition to the supporting substrate and drying it to form an adhesive layer can be employed. Alternatively, a method (transfer method) may be employed in which an adhesive layer is formed on a surface having peelability (release surface) by applying an adhesive composition and drying the adhesive layer, and the adhesive layer is transferred to a supporting base material. As the release surface, for example, the surface of a release liner described later can be preferably used. In addition, although the pressure-sensitive adhesive layer disclosed herein is typically formed continuously, it is not limited to such a form, and may be a pressure-sensitive adhesive layer formed in a regular or random pattern such as a dot shape or a stripe shape, for example.

Application of the pressure-sensitive adhesive composition can be performed using a conventionally known coater such as a gravure roll coater, a die coater, or a bar coater, for example. Alternatively, the pressure-sensitive adhesive composition may be applied by impregnation or curtain coating.

It is preferable to dry the adhesive composition under heating from viewpoints of accelerating the crosslinking reaction and improving production efficiency. The drying temperature can be, for example, about 40 to 150°C, preferably about 60 to 130°C. After the pressure-sensitive adhesive composition is dried, aging may be further performed for the purpose of adjusting migration of components within the pressure-sensitive adhesive layer, progressing a crosslinking reaction, relieving strain that may exist within the pressure-sensitive adhesive layer, and the like.

The pressure-sensitive adhesive layer disclosed herein may have a single layer structure or may have a multilayer structure of two or more layers. From viewpoints of productivity and the like, it is preferable that the pressure-sensitive adhesive layer has a single-layer structure.

The thickness of the pressure-sensitive adhesive layer is not particularly limited. From the viewpoint of avoiding excessive thickness of the PSA sheet, the thickness of the PSA layer is suitably about 100 μm or less, preferably about 70 μm or less, and more preferably about 50 μm or less. The thickness of the pressure-sensitive adhesive layer can be about 35 μm or less, for example, about 25 μm or less, or even about 15 μm or less. A pressure-sensitive adhesive layer having a limited thickness can be one that satisfies the request for thinning and lightening. The lower limit of the thickness of the pressure-sensitive adhesive layer is not particularly limited, and from the viewpoint of adhesion to the adherend, it is advantageous to set it to about 1 μm or more, and it is appropriate to set it to about 3 μm or more, preferably about 10 μm or more, and more It is preferably about 15 μm or more, more preferably about 20 μm or more, may be about 30 μm or more, about 35 μm or more, or about 40 μm or more. By setting it to a predetermined thickness or more, a light transmittance of a predetermined value or less and L ^* within a predetermined range can be preferably realized. In addition, it is easy to obtain desired adhesive properties (adhesive strength, impact resistance, etc.).

<Support Substrate>

In the aspect in which the PSA sheet disclosed herein is in the form of a single-sided or double-sided PSA sheet with a base material, the base material for supporting (backing) the PSA layer is a resin film, paper, cloth, rubber sheet, foam sheet, or metal foil , complexes thereof, and the like can be used. Examples of resin films include polyolefin films such as polyethylene (PE), polypropylene (PP), and ethylene/propylene copolymers; polyester films such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene naphthalate (PEN); Vinyl chloride resin film; Vinyl acetate resin film; polyimide resin film; polyamide resin film; fluororesin film; Cellophane etc. are mentioned. Examples of the paper include washi paper, kraft paper, glassine paper, fine paper, synthetic paper, and top-coated paper. Examples of fabrics include woven fabrics and nonwoven fabrics obtained by single or mixed spinning of various fibrous substances. Examples of the fibrous material include cotton, staple fiber, Manila hemp, pulp, rayon, acetate fiber, polyester fiber, polyvinyl alcohol fiber, polyamide fiber, and polyolefin fiber. Examples of rubber sheets include natural rubber sheets and butyl rubber sheets. Examples of the foam sheet include a foamed polyurethane sheet and a foamed polychloroprene rubber sheet. Aluminum foil, copper foil, etc. are mentioned as an example of metal foil.

In addition, the nonwoven fabric referred to herein is a concept indicating a nonwoven fabric for adhesive sheets mainly used in the field of adhesive tapes and other adhesive sheets, and is a nonwoven fabric typically produced using a general paper machine (so-called 'paper'). in some cases). In addition, a resin film here is typically a non-porous resin sheet, and is a concept different from, for example, nonwoven fabrics and woven fabrics (in other words, a concept excluding nonwoven fabrics and woven fabrics). Any of a non-stretched film, a uniaxially stretched film, and a biaxially stretched film may be sufficient as the said resin film.

As the supporting substrate constituting the PSA sheet with a substrate, a substrate containing a resin film as a base film can be preferably used. The base film is typically a (independent) member capable of independently maintaining its shape. The supporting substrate in the technology disclosed herein may be substantially composed of such a base film. Alternatively, the supporting substrate may include an auxiliary layer in addition to the base film. Examples of the auxiliary layer include a colored layer, a reflective layer, an undercoat layer, and an antistatic layer provided on the surface of the base film.

The resin film is a film containing a resin material as a main component (for example, a component contained in the resin film in an amount exceeding 50% by weight). From the viewpoints of handleability and workability, a polyester film is preferred, and among these, a PET film is particularly preferred.

The supporting substrate may have transparency, or may have light-shielding properties or photosensitivity. In some embodiments, a colorant may be contained in the supporting substrate (such as a resin film). In this way, the light transmittance (light shielding property) of the supporting substrate can be adjusted. Adjusting the light transmittance (for example, vertical light transmittance) of the supporting substrate may be helpful in adjusting the light transmittance of the supporting substrate and, consequently, the light transmittance of the pressure-sensitive adhesive sheet including the substrate.

As a coloring agent, a conventionally well-known pigment or dye can be used similarly to the coloring agent which can be made to contain in an adhesive layer. The colorant is not particularly limited, and may be, for example, a colorant such as black, gray, white, red, blue, yellow, green, yellow-green, orange, purple, gold, silver, or pearl.

In some aspects, a black colorant can be preferably used as the colorant for the supporting base material in that the light-shielding property (for example, vertical light transmittance) can be efficiently adjusted with a small amount of the colorant. As a specific black coloring agent, what was illustrated as a coloring agent which can be made to contain in an adhesive layer is mentioned. In some preferred embodiments, a pigment (for example, a particulate black colorant such as carbon black) having an average particle diameter of 10 nm to 500 nm, more preferably 10 nm to 120 nm can be used.

The amount of the colorant used in the supporting substrate (eg, resin film) is not particularly limited, and can be appropriately adjusted so as to impart desired optical properties. The amount of the colorant used is suitably about 0.1 to 30% by weight of the weight of the supporting substrate, for example, 0.1 to 25% by weight (typically 0.1 to 20% by weight).

Various additives such as fillers (inorganic fillers, organic fillers, etc.), dispersants (surfactants, etc.), anti-aging agents, antioxidants, ultraviolet absorbers, antistatic agents, lubricants, plasticizers, etc. may be mixed. The compounding ratio of various additives is about less than 30% by weight (for example, less than 20% by weight, typically less than 10% by weight).

The support substrate (eg, resin film) may have a single-layer structure, or may have a two-layer, three-layer or higher multilayer structure. From the standpoint of shape stability, the supporting substrate preferably has a single-layer structure. In the case of a multilayer structure, it is preferable that at least one layer (preferably all layers) is a layer having a continuous structure of the above resin (e.g., polyester-based resin). The manufacturing method of a support base material (typically, a resin film) should just employ|adopt a conventionally well-known method suitably, and it is not specifically limited. For example, conventionally known general film forming methods such as extrusion molding, inflation molding, T-die cast molding, and calender roll molding can be appropriately employed.

The supporting substrate may be colored by a colored layer disposed on the surface of a base film (preferably a resin film). In a base material having a configuration including a base film and a colored layer, the base film may or may not contain a colorant. The said colored layer may be arrange|positioned on either surface of a base film, and may be arrange|positioned on both surfaces, respectively. In the configuration in which colored layers are respectively disposed on both surfaces of the base film, the configurations of the colored layers may be the same or different.

Such a colored layer can typically be formed by applying a composition for forming a colored layer containing a coloring agent and a binder to a base film. As a coloring agent, a conventionally well-known pigment or dye can be used similarly to the coloring agent which can be made to contain an adhesive layer or a resin film. As the binder, materials known in the field of paint or printing can be used without particular limitation. For example, polyurethane, phenol resin, epoxy resin, urea melamine resin, polymethyl methacrylate and the like are exemplified. The composition for forming a colored layer may be, for example, a solvent type, an ultraviolet curing type, or a thermosetting type. The formation of the colored layer can be performed by employing a means conventionally used for forming the colored layer without particular limitation. For example, a method of forming a colored layer (printed layer) by printing such as gravure printing, flexographic printing, and offset printing can be preferably employed.

The colored layer may have a single-layer structure consisting entirely of one layer, or may have a multilayer structure including two, three or more sub-colored layers. A colored layer having a multilayer structure including two or more layers of sub colored layers can be formed, for example, by repeatedly applying (for example, printing) a composition for forming a colored layer. The color and compounding amount of the colorant contained in each sub colored layer may be the same or different. In the colored layer for imparting light-shielding properties, it is particularly meaningful to have a multilayer structure from the viewpoint of preventing the occurrence of pinholes and enhancing the reliability of light leakage prevention.

The thickness of the entire colored layer is suitably about 1 μm to 10 μm, preferably about 1 μm to 7 μm, and, for example, about 1 μm to 5 μm. In the colored layer including two or more sub-colored layers, the thickness of each sub-colored layer is preferably about 1 μm to 2 μm.

The thickness of the supporting substrate is not particularly limited. From the viewpoint of avoiding excessive thickness of the pressure-sensitive adhesive sheet, the thickness of the supporting substrate can be, for example, about 200 μm or less (for example, about 100 μm or less). Depending on the purpose of use or usage mode of the PSA sheet, the thickness of the supporting substrate may be about 70 μm or less, about 30 μm or less, or about 15 μm or less (for example, about 8 μm or less). The lower limit of the thickness of the supporting substrate is not particularly limited. From the standpoint of handling (handling) and processability of the PSA sheet, the thickness of the supporting substrate is suitably about 2 μm or more, and preferably about 5 μm or more, for example about 10 μm or more.

The surface of the supporting substrate may be subjected to a conventionally known surface treatment such as corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, or application of an undercoat agent. Such a surface treatment may be a treatment for improving the adhesion between the support base material and the pressure-sensitive adhesive layer, in other words, the anchoring property of the pressure-sensitive adhesive layer to the support base material.

Further, when the technique disclosed herein is implemented in the form of a single-sided pressure-sensitive adhesive sheet with a base material, the back surface of the supporting base material may be subjected to peeling treatment as needed. The peeling treatment may be, for example, a treatment in which a general silicone-based, long-chain alkyl-based, fluorine-based, or other peeling agent is typically applied in a thin film form of about 0.01 μm to 1 μm (for example, 0.01 μm to 0.1 μm). By performing such a peeling treatment, effects such as facilitating rewinding of a wound body obtained by winding an adhesive sheet in a roll shape can be obtained.

<Releasable liner>

In the technique disclosed herein, a release liner can be used in the case of formation of the pressure-sensitive adhesive layer, production of the pressure-sensitive adhesive sheet, storage of the pressure-sensitive adhesive sheet before use, circulation, shape processing, and the like. The release liner is not particularly limited, and examples thereof include a release liner comprising a release treatment layer on the surface of a liner substrate such as a resin film or paper, a fluorine-based polymer (polytetrafluoroethylene, etc.) or a polyolefin-based resin (polyethylene, poly A release liner containing a low adhesive material such as propylene or the like can be used. The release treatment layer may be formed by surface treatment of the liner substrate with a release treatment agent such as silicon, long-chain alkyl, fluorine, or molybdenum sulfide.

<Characteristics of adhesive sheet, etc.>

(adhesiveness)

The 180-degree peel strength (adhesive strength) of the PSA sheet disclosed herein is not limited to a specific range because it may vary depending on the purpose of use or application area. From the viewpoint of obtaining good adhesion to adherends, the adhesive strength of the pressure-sensitive adhesive sheet is suitably, for example, about 1.0 N/25 mm or more, preferably about 5.0 N/25 mm or more, more preferably about 10 N/25 mm or more. , More preferably, it is about 12 N/25 mm or more, and may be about 15 N/25 mm or more. According to the technology disclosed herein, the above-described adhesive force can be realized while the pressure-sensitive adhesive layer has a light transmittance of a predetermined value or less and L ^* within a predetermined range. The upper limit of the adhesive force is not particularly limited, and may be about 30 N/25 mm or less (eg, 25 N/25 mm or less). The adhesive force can be measured by the method described in Examples described later. In the case of a double-sided pressure-sensitive adhesive sheet having adhesive surfaces on both sides, the adhesive force on each surface may be the same or different.

(shear adhesion)

Although not particularly limited, the pressure-sensitive adhesive sheet disclosed herein preferably exhibits, for example, a shear adhesive force of 1.0 MPa or more. A pressure-sensitive adhesive sheet exhibiting such a shear adhesive force exhibits strong resistance to a force (ie, shear force) that tends to displace the adhesive interface, and thus has excellent adherend retention performance. From the viewpoint of exhibiting higher holding performance, the shear adhesive strength of the pressure-sensitive adhesive sheet is preferably 1.8 MPa or more, more preferably 2.0 MPa or more, still more preferably 2.2 MPa or more. The upper limit of the shear adhesive force is not particularly limited, and generally higher is preferable. On the other hand, from the viewpoint of facilitating realization of a light transmittance of a predetermined value or less and a predetermined range of L ^* , in some embodiments, the shear adhesive force may be, for example, 20 MPa or less, 10 MPa or less, or 5 MPa or less. It may be 3 MPa or less. The shear adhesive strength can be measured by the method described in the examples described later.

(light transmittance)

Although not particularly limited, the pressure-sensitive adhesive sheet preferably has a light transmittance of 20% or less. Such an adhesive sheet is suitable for concealing the adherend and adjusting the appearance of the adherend through the adhesive sheet (for example, suppression of unevenness in appearance), and can impart design. The light transmittance of the pressure-sensitive adhesive sheet may be 18% or less, and in some preferred embodiments, the light transmittance of the pressure-sensitive adhesive sheet may be less than 12%, may be less than 10%, may be less than 8.0%, may be less than 6.0%, may be less than 4.0% It may be less than 3.0%. The lower the light transmittance, the better the hiding property. The lower limit of the light transmittance is not particularly limited, and may be substantially 0%, that is, below the detection limit, may be 0.05% or more, may be 0.1% or more, may be 1.0% or more, may be 2.0% or more, or may be 5.0% or more. may be continued In some aspects, the light transmittance of the pressure-sensitive adhesive sheet is 8.0% or more, and may be 12% or more (for example, 15% or more). By having a certain degree of light transmittance, the adherend can be appropriately concealed, the appearance of the adherend (for example, a metal material) can be adjusted, or a design that retains the texture of the adherend can be imparted. Further, in an adhesive sheet having a light transmittance equal to or greater than the predetermined value, in other words, an adhesive sheet that transmits light to a certain extent, the effect of setting L ^* in the range of 20 or more and 70 or less (by setting the color tone to be similar to that of the adherend) suppression of concealment non-uniformity) is preferably exerted. A pressure-sensitive adhesive sheet having moderate light transmission is preferable also from the viewpoint of maintaining adhesive properties, productivity, and the like.

The light transmittance of the pressure-sensitive adhesive sheet can be measured by the method described in Examples described later. The light transmittance of the pressure-sensitive adhesive sheet can be adjusted depending on the pressure-sensitive adhesive-containing component (for example, the type or amount of colorant (preferably black colorant) used), the substrate-containing component, the thickness of each layer, and the like.

(L ^* a ^* b ^* colorimetric characteristics)

It is preferable that the pressure-sensitive adhesive sheet typically has L ^* defined in the L ^* a ^* b ^* color system of 20 or more and 70 or less. By using an adhesive sheet that satisfies this characteristic, even when processing is applied to the adhesive sheet sticking surface of the adherend, the contrast with the processed portion becomes less conspicuous by concealing the adherend, and Concealment non-uniformity is suppressed. The L ^* may vary depending on the color of the adherend, but in some embodiments, it is usually 50 or less, preferably 48 or less, more preferably 45 or less, still more preferably 42 or less. Further, the L ^* is preferably 30 or more, more preferably 35 or more, still more preferably 40 or more. For example, when the material constituting the adhesive sheet sticking surface of the adherend is stainless steel or aluminum, it is suitable to set it as the range of L ^* mentioned above. In some other aspects, L ^* is preferably 65 or less, may be 62 or less, 60 or less, 58 or less, or 56 or less (for example, 52 or less). In some of the other aspects described above, L ^* may be greater than 45, greater than 50, or greater than 54 (for example, greater than 55). According to such an aspect, the adherend can be satisfactorily concealed using the diffused light in the pressure-sensitive adhesive sheet.

Although not particularly limited, the pressure-sensitive adhesive sheet preferably has both a ^* and b ^* defined in the L ^* a ^* b ^* color system within a predetermined range. In such a pressure-sensitive adhesive sheet having color, the effect of the technique disclosed herein is preferably exhibited. In addition, if the chromaticities a ^* and b ^* are within a predetermined range, it is easy to match the color of the adherend or the member surrounding the adherend. From such a point of view, the a ^* is preferably -15 or more, preferably -10 or more, more preferably -5 or more, still more preferably -1 or more (eg -0.3 or more), and 15 or less is appropriate, preferably 10 or less, more preferably 5 or less, still more preferably 1 or less (for example, 0.3 or less). From the same point of view, the b ^* is preferably -15 or more, preferably -10 or more, more preferably -5 or more, even more preferably -3 or more (e.g. -2 or more), and also 15 The following is appropriate, preferably 10 or less, more preferably 5 or less, still more preferably 3 or less (for example, 2 or less).

Each value of L ^* a ^* b ^* of the pressure-sensitive adhesive sheet can be measured by the method described in Examples described later. Each value of L ^* a ^* b ^* of the pressure-sensitive adhesive sheet can be adjusted depending on the pressure-sensitive adhesive-containing component (for example, the type or amount of colorant (eg, white colorant, preferably metal oxide)) or base material-containing component.

In the case of a double-sided pressure-sensitive adhesive sheet having adhesive surfaces on both sides, each value of L ^* a ^* b ^* of each surface (each adhesive surface, first adhesive surface, and second adhesive surface) may be the same or different.

(light reflectance)

In addition, it is preferable that the light reflectance of the adhesive sheet is 8.0% or more. In addition to limiting the light transmittance of the pressure-sensitive adhesive layer, the light reflectance on the surface of the pressure-sensitive adhesive sheet is set to 8% or more, the light is reflected on the pressure-sensitive adhesive surface and the light entering the pressure-sensitive adhesive is reduced. of optical control is compatible. The light reflectance of the pressure-sensitive adhesive sheet is preferably 9.0% or more, more preferably 10% or more, still more preferably 12% or more, and may be 14% or more (for example, 16% or more). In some embodiments, the light reflectance may be 18% or higher, or 22% or higher (for example, 25% or higher). Since the upper limit of the light reflectance is set in an appropriate range in relation to the light transmittance, it is not limited to a specific range, and is, for example, less than 40%, may be 30% or less, may be 25% or less, may be 20% or less (for example, 15% or less).

The light reflectance of the pressure-sensitive adhesive sheet can be measured by the method described in Examples described later. The light reflectance of the pressure-sensitive adhesive sheet can be adjusted according to the components containing the adhesive (for example, the type or amount of colorant (preferably metal oxide)) or the component containing the substrate.

In the case of a double-sided pressure-sensitive adhesive sheet having adhesive surfaces on both sides, the light reflectance of each surface (each adhesive surface, first adhesive surface, and second adhesive surface) may be the same or different.

The light transmittance and light reflectance of the pressure-sensitive adhesive sheet are not particularly limited. For example, the ratio (R/T) of light reflectance (R) to light transmittance (T) of the pressure-sensitive adhesive sheet is suitably 0.4 or more, preferably 0.5 or more, more preferably 1.0 or more, and 2.0 or more may be sufficient. Also, the upper limit of the ratio (R/T) may be about 10 or less, for example 5 or less. In an aspect in which a certain degree of light transmittance is required of the pressure-sensitive adhesive sheet, the ratio (R/T) may be less than 3, may be less than 2, or may be less than 1.

(total thickness)

The total thickness of the pressure-sensitive adhesive sheet disclosed herein (in a configuration including a pressure-sensitive adhesive layer and a support substrate, a support substrate is further included, but a release liner is not included.) is not particularly limited. The total thickness of the adhesive sheet can be, for example, about 300 μm or less, and from the viewpoint of thinning, about 200 μm or less is appropriate, and may be about 100 μm or less (for example, about 70 μm or less). In some preferred embodiments, the pressure-sensitive adhesive sheet may have a thickness of about 50 μm or less, and may be, for example, about 35 μm or less. The lower limit of the thickness of the pressure-sensitive adhesive sheet is not particularly limited, but may be about 1 μm or more, for example about 3 μm or more, preferably about 6 μm or more, more preferably about 10 μm or more (e.g. about 15 μm or more), more preferably about 20 μm or more. A pressure-sensitive adhesive sheet having a thickness equal to or greater than a predetermined value tends to have good handleability and excellent adhesiveness and impact resistance. In addition, in the base-free PSA sheet, the thickness of the PSA layer becomes the total thickness of the PSA sheet.

<Use>

The PSA sheet disclosed herein is suitable for various applications requiring the concealability of the PSA sheet. For example, among electronic devices such as portable electronic devices, there are some that require the use of an adhesive sheet to conceal members or adjust appearance. For such an electronic device, the adhesive sheet disclosed herein is suitable.

Non-limiting examples of the portable electronic devices include mobile phones, smart phones, tablet PCs, notebook PCs, and various wearable devices (eg, wrist wear type worn on the wrist such as a wrist watch, clip or strap, etc. Modular type to be attached to a part, eyewear type including glasses type (monocular or binocular type, including head-mounted type), clothing type to be attached to shirts, socks, hats, etc. in the form of accessories, such as earphones, to be worn on ears ear-wear type, etc.), digital cameras, digital video cameras, audio devices (portable music players, IC recorders, etc.), calculators (electronic desk calculators, etc.), portable game devices, electronic dictionaries, electronic notebooks, electronic books, in-vehicle use This includes information devices, portable radios, portable TVs, portable printers, portable scanners, and portable modems. Further, in this specification, 'carrying' means not being able to simply carry, but having a level of portability that can be carried relatively easily by an individual (standard adult). In addition, as an example of the said electronic device, a PC (desktop type, notebook type, tablet type, etc.), TV, etc. are mentioned. These may incorporate a display device (display device) such as liquid crystal or organic EL.

The adhesive sheet disclosed herein may be used for the purpose of fixing a member other than a pressure sensor in a portable electronic device having a pressure sensor among the portable electronic devices. In some aspects, the adhesive sheet includes a device for indicating a position on the screen (typically a pen-type or mouse-type device) and a device for detecting the position, and a plate corresponding to the screen (typically a touch panel) In an electronic device (typically a portable electronic device) having a function enabling absolute positioning on the image, it can be used to fix the pressure sensor and other members.

In addition, the adhesive sheet disclosed herein is suitable for use disposed on the back side of a display screen (display unit) such as a touch panel display in a portable electronic device. By disposing the adhesive sheet disclosed herein on the back side of the display screen (display unit), deterioration in visibility of the display screen can be prevented regardless of how the portable electronic device is used.

In addition, the adhesive sheet disclosed herein is suitable for a portable electronic device having a built-in optical sensor. Various devices such as the above-mentioned portable electronic devices are optical sensors using infrared rays, visible rays, and ultraviolet rays for the purpose of operating devices, sensing nearby objects, detecting ambient brightness (environmental light), and data communication. can be provided. Although not particularly limited, examples of the light sensor include an acceleration sensor, a proximity sensor, a luminance sensor (ambient light sensor), and the like. Such an optical sensor may include a light receiving element for light rays such as ultraviolet rays, visible rays, and infrared rays, and may also include a light emitting element for specific rays such as infrared rays. In other words, the optical sensor may include a light emitting element and/or a light receiving element of a specific wavelength region among wavelength regions including ultraviolet rays, visible rays, and infrared rays. For such a device, by applying a configuration according to a preferred embodiment of the technology disclosed herein, the light in the device is controlled by limiting the incident light that can be refracted and scattered in the pressure-sensitive adhesive layer, thereby reducing the operating accuracy of the sensor can prevent

The material (adherent material) to which the PSA sheet disclosed herein is affixed is not particularly limited, but examples thereof include copper, silver, gold, iron, tin, palladium, aluminum, nickel, titanium, chromium, zinc, etc. Metal materials such as alloys containing two or more types, for example, polyimide-based resins, acrylic resins, polyethernitrile-based resins, polyethersulfone-based resins, polyester-based resins (PET-based resins, polyethylene naphthalate-based resins, etc.) Various resin materials such as polyvinyl chloride-based resins, polyphenylene sulfide-based resins, polyether ether ketone-based resins, polyamide-based resins (so-called aramid resins, etc.), polyarylate-based resins, polycarbonate-based resins, liquid crystal polymers ( Typically, inorganic materials such as plastic materials), alumina, zirconia, soda glass, quartz glass, and carbon. Among them, metal materials such as copper, aluminum, and stainless steel, polyester-based resins such as PET, and resin materials (typically plastic materials) such as polyimide-based resins, aramid resins, and polyphenylene sulfide-based resins are used. It is widely used. The above material may be a material of a member constituting a product such as an electronic device. The pressure-sensitive adhesive sheet disclosed herein can be used by being attached to a member made of the above material. In addition, the above material may be a material constituting a fixed object such as the pressure-sensitive sensor or the display unit (for example, a back member such as an electromagnetic shield or a reinforcing plate). In addition, an object to be fixed refers to an object to which the pressure-sensitive adhesive sheet is affixed, that is, an adherend. Further, the rear member refers to a member disposed on the opposite side of the front face (visible side) of the pressure-sensitive sensor or the display unit in, for example, a portable electronic device, and is disposed on the rear face of the display device 200 shown in FIG. 4 described later. It may be a member constituting the support portion 240 to be. In addition, the object to be fixed may have either a single-layer structure or a multi-layer structure, and various surface treatments may be applied to the surface (sticking surface) to which the pressure-sensitive adhesive sheet is applied. Although not particularly limited, as an example of an object to be fixed, a back member having a thickness of about 1 μm or more (typically 5 μm or more, such as 60 μm or more, and even 120 μm or more) and 1500 μm or less (for example, 800 μm or less) can be heard

In addition, the pressure-sensitive adhesive sheet disclosed herein is suitable for concealing the surface of a processed adherend. The surface of the adherend includes, for example, a processed portion (which may be a perforated portion) subjected to processing such as perforation, and the adhesive sheet disclosed herein is applied to a region including such a processed portion to conceal it. The good concealment property in which concealment nonuniformity was suppressed is realized. Since the PSA sheet disclosed herein can exhibit good hiding properties regardless of whether the adherend is processed or not, there are few restrictions on the application site of the PSA sheet and its usability is excellent. The adherend subjected to processing such as perforation is, for example, a member or article having a surface (adhesive sheet sticking surface) formed of a metal material such as aluminum or stainless steel. Suitable examples include stainless steel members, aluminum members, and the like A metal member is mentioned. Such a metal member may be, for example, a member constituting the support portion 240 of the display device 200 shown in FIG. 4 to be described later. Further, in an aspect in which the pressure-sensitive adhesive sheet is a double-sided pressure-sensitive adhesive sheet and different adherends (members or articles) are affixed on each side thereof, one adherend only needs to include a processing portion on its surface.

In the PSA sheet disclosed herein, the color difference between a member or material to which it is applied (one adherend in the case of a double-sided PSA sheet, preferably a metal member made of stainless steel or the like) and the PSA sheet is limited within a predetermined range. desirable. As a result, in the case where the adhesive sheet is used to cover the adherend, the concealment unevenness is suppressed even when processing is applied to the adhesive sheet sticking surface of the adherend. From such a viewpoint, in some aspects, ΔE ^* , which is an index of the color difference between the pressure-sensitive adhesive sheet and the adherend, is 20 or less, preferably 16 or less, and may be 12 or less (for example, 10 or less). In some preferred embodiments, ΔE ^* , which is an index of the color difference between the pressure-sensitive adhesive sheet and the adherend, is 5.0 or less, more preferably 2.5 or less, still more preferably 1.2 or less. Further, the lower limit of ΔE ^* may be about 0.2 or more, which is the colorimetric reproduction accuracy of the same object, may be more than 0.6, or may be more than 1.2. ΔE ^* can be obtained by the method described in Examples described later.

The color tone of the member or material to which the PSA sheet disclosed herein is applied (in the case of the double-sided PSA sheet, at least one of the adherends, preferably a metal member made of stainless steel or the like) is not particularly limited. E ^* , which is an index of the color of the surface of the complex material, can usually be in the range of 20 to 70. Here, E ^* of the surface of the adherend material is:

E ^* =[(L ^* ) ² +(a ^* ) ² +(b ^* ) ² ] ^1/2

can be obtained from Each value of L ^* a ^* b ^* in the formula is a value of L ^* a ^* b ^* on the surface of the adherend material measured using a color difference meter based on JIS Z8781-4:2013. From the viewpoint of preferably realizing the effect of the technique disclosed herein, the above E ^* is preferably 30 or more, more preferably 35 or more, still more preferably 38 or more (for example, 40 or more), and 50 Below is suitable, Preferably it is 48 or less, More preferably, it is 45 or less, More preferably, it is 42 or less. In the PSA sheet disclosed herein, by hiding the adherend material having E ^* within the above range, adjusting the L ^* of the PSA layer to obtain a color similar to that of the adherend material surface, the adhesive sheet sticking surface of the adherend is processed. Even in the case where this is implemented, the concealment nonuniformity can be suppressed.

Further, the member or material to which the PSA sheet is applied (at least one adherend in the case of a double-sided PSA sheet) may have light transmission properties. According to the technology disclosed herein, it is possible to cover the surface of the adherend with the adhesive sheet over the light-transmitting adherend as described above (specifically, with the double-sided adhesive sheet, conceal the surface of the adherend on the other side). The light transmittance of the adherend having light transmittance may be, for example, greater than 50% or greater than 70%. In some preferred embodiments, the adherend has a light transmittance of 80% or more, more preferably 90% or more, and may be 95% or more (for example, 95 to 100%). Such a material may be a resin film (for example, a polyester-based resin film such as PET film) disposed on the back surface of an image display unit of various devices such as portable electronic devices. The pressure-sensitive adhesive sheet disclosed herein can be preferably used in an aspect of sticking to an adherend (eg, member) having a light transmittance of a predetermined value or more. The light transmittance may be measured in the same way as the light transmittance of the pressure-sensitive adhesive layer.

From the above, according to the technique disclosed herein, a laminate comprising a pressure-sensitive adhesive sheet and a member to which the pressure-sensitive adhesive sheet is attached is provided. In some embodiments, a laminate including a pressure-sensitive adhesive sheet is a laminate including the pressure-sensitive adhesive sheet and a metal member (first member). A metal member includes a processing part in which processing was performed on the surface thereof. Further, in some embodiments, an adherend material having the light transmittance described above is affixed to the side of the pressure-sensitive adhesive sheet opposite to the surface to which the metal member is affixed. In this aspect, the laminate is a laminate comprising a metal member (first member), an adhesive sheet, and a light-transmitting member (second member) in this order. In addition, the said adhesive sheet is also called the adhesive layer in a laminated body.

An example of the structure of the laminate is shown in FIGS. 2 and 3 . A laminate 50 shown in FIG. 2 includes a substrate-free adhesive sheet 1 and a first member 41 . Specifically, in the laminate 50 , one adhesive surface (first adhesive surface) 1A of the substrate-free adhesive sheet 1 is adhered to the first member 41 . In this embodiment, the PSA sheet 1 is a substrate-free double-sided PSA sheet made of the PSA layer 21 . Moreover, the 1st member 41 is provided with perforation as the processing part 42. In the PSA sheet 1, since the light transmittance of the PSA layer 21 thereof is 20% or less and L ^* is in the range of 20 to 70, as shown in FIG. 3, when viewed from the top surface (the second member side), The surface of the 1st member 41, including the process part 42, is concealed satisfactorily with little concealment unevenness. In this embodiment, the laminate 50 further includes a second member 45 bonded to the other adhesive surface (second adhesive surface) 1B of the adhesive sheet 1 . Both the first member 41 and the second member 45 have a sheet-like or plate-like shape, and the laminate 50 has a multilayer structure. In this embodiment, the second member 45 is a member having light transmission properties (a member having transparency). In this embodiment, only the first member 41 is processed, but the second member 45 or the adhesive sheet 1 may be provided with a hole or other processed portion. About the details of the member which comprises a laminated body, since it is as having demonstrated the above-mentioned member, material, and adherend, overlapping description is not repeated.

In some preferred aspects, the first member 41 is a metal member, and the metal material exemplified as the above-mentioned adherend material is used. The metal member as the first member 41 is preferably an aluminum member or a stainless steel member, and more preferably a stainless steel member. By attaching the PSA sheet 1 disclosed herein to the surface of the metal member as the first member 41 including the processed portion 42, the metal member can be satisfactorily concealed. Such a metal member may be, for example, a member constituting the support portion 240 of the display device 200 shown in FIG. 4 to be described later.

Further, as described above, in a preferred embodiment, the second member 45 is a light-transmitting member, and has the light transmittance of the light-transmitting adherend described above. The second member 45 is preferably a member made of a resin film, more preferably a polyester-based resin film (more specifically, a PET-based resin film). The second member 45 may be, for example, a member disposed on the back side of the display unit in the display device. In the aspect in which the adhesive sheet 1 is attached to the light-transmitting member as the second member 45, the first member 41 is covered by the adhesive sheet 1 when viewed from the side of the second member 45. The laminate 50 as described above may typically be a component of an organic EL display device or a liquid crystal display device. The laminate 50 is suitable for use disposed on the back side of an image display unit (it may be a display unit such as a touch panel display) of various devices such as portable electronic devices, for example.

Since the adhesive sheet disclosed herein has limited light transmittance and may have excellent light blocking properties in some embodiments, various light sources such as LEDs (light emitting diodes) or light emitting elements such as self-emitting organic ELs It is preferably used in an electronic device comprising a. For example, it can be suitably used for electronic devices (typically portable electronic devices) equipped with an organic EL display device or a liquid crystal display device requiring predetermined optical properties.

4 is an exploded perspective view schematically illustrating a configuration example of a display device. As shown in FIG. 4 , the display device 200 included in the portable electronic device 100 includes a display portion 220 composed of a cover member, an organic EL unit, or the like, and a support portion 240 . The display device 200 is configured to further include an adhesive sheet 230 . In this configuration example, the adhesive sheet 230 is in the form of a double-sided adhesive sheet (double-sided adhesive sheet) for fixing the members constituting the display unit 220 and the support unit 240 . Further, the support portion 240 includes a substrate (a metal plate such as a stainless steel plate or an aluminum plate) and the like. The adhesive sheet disclosed herein is preferably used as a component of the display device as described above.

Matters disclosed by this specification include the following.

[1] A display device including a display unit including a cover member and an organic EL unit, and a support unit,

An adhesive sheet is bonded to the support portion,

The pressure-sensitive adhesive sheet includes a pressure-sensitive adhesive layer,

The display device, wherein the pressure-sensitive adhesive layer has a light transmittance of 20% or less, and L ^* defined in the L ^* a ^* b ^* color system is 20 or more and 70 or less.

[2] The back member includes a processed metal member,

The display device according to [1] above, wherein the adhesive sheet is attached to a region including a processed portion of the metal member.

[3] In the pressure-sensitive adhesive layer, the display device according to [1] or [2] above, wherein a ^* and b ^* defined in the L ^* a ^* b ^* color system are both within the range of -10 or more and +10 or less. .

[4] The display device according to any one of [1] to [3], wherein the pressure-sensitive adhesive layer contains a black colorant as the first colorant and a metal oxide as the second colorant.

[5] The display device according to [4] above, wherein the content of the metal oxide in the pressure-sensitive adhesive layer is 1% by weight or more and 6% by weight or less.

[6] The display device according to [4] or [5] above, wherein the content of the black colorant in the pressure-sensitive adhesive layer is less than 2% by weight.

[7] In any one of [4] to [6], the weight ratio (C1/C2) of the amount of the first colorant (C1) and the amount of the second colorant (C2) is in the range of 0.01 to 0.30. indicated display device.

[8] The display device according to any one of [1] to [7] above, wherein the pressure-sensitive adhesive layer is an acrylic pressure-sensitive adhesive layer containing an acrylic polymer as a base polymer.

[9] The display device according to any one of [1] to [8] above, wherein the pressure-sensitive adhesive layer has a thickness in the range of 10 to 50 μm.

[10] The display device according to any one of [1] to [9] above, wherein the pressure-sensitive adhesive sheet is a substrate-free double-sided adhesive pressure-sensitive adhesive sheet containing the pressure-sensitive adhesive layer.

[11] A pressure-sensitive adhesive sheet containing a pressure-sensitive adhesive layer,

The pressure-sensitive adhesive layer has a light transmittance of 20% or less, and L ^* defined in the L ^* a ^* b ^* color system is 20 or more and 70 or less.

[12] The pressure-sensitive adhesive sheet according to [11], wherein a ^* and b ^* defined in the L ^* a ^* b ^* color system are both within the range of -10 or more and +10 or less.

[13] The pressure-sensitive adhesive sheet according to [11] or [12], wherein the pressure-sensitive adhesive layer contains a black colorant as the first colorant and a metal oxide as the second colorant.

[14] The pressure-sensitive adhesive sheet according to [13] above, wherein the content of the metal oxide in the pressure-sensitive adhesive layer is 1% by weight or more and 6% by weight or less.

[15] The pressure-sensitive adhesive sheet according to [13] or [14], wherein the content of the black colorant in the pressure-sensitive adhesive layer is less than 2% by weight.

[16] In any one of [13] to [15], the weight ratio (C1/C2) of the amount of the first colorant (C1) and the amount of the second colorant (C2) is in the range of 0.01 to 0.30. The adhesive sheet described.

[17] The PSA sheet according to any one of [11] to [16], which is a substrate-free double-sided adhesive PSA sheet containing the PSA layer.

[18] The pressure-sensitive adhesive sheet according to any one of [11] to [17], wherein the light reflectance of the pressure-sensitive adhesive layer is 8% or more.

[19] The pressure-sensitive adhesive sheet according to any one of [11] to [18], wherein the pressure-sensitive adhesive layer is an acrylic pressure-sensitive adhesive layer containing an acrylic polymer as a base polymer.

[20] The pressure-sensitive adhesive sheet according to any one of [11] to [19], wherein the pressure-sensitive adhesive layer has a thickness in the range of 10 to 50 μm.

[21] The pressure-sensitive adhesive sheet according to any one of [11] to [20] above, which is applied to a region including a processed portion of a processed metal member.

[22] The adhesive sheet according to any one of [11] to [20] above, which is used for joining members in portable electronic devices.

[23] The adhesive sheet according to any one of [11] to [22] above, which is used for joining metal members in portable electronic devices.

[24] A laminate comprising a metal member (first member) and an adhesive sheet,

The pressure-sensitive adhesive sheet includes a pressure-sensitive adhesive layer,

The laminate wherein the pressure-sensitive adhesive layer has a light transmittance of 20% or less, and L ^* defined in the L ^* a ^* b ^* color system is 20 or more and 70 or less.

[25] A laminate comprising a light-transmitting member (second member) and an adhesive sheet,

The pressure-sensitive adhesive sheet includes a pressure-sensitive adhesive layer,

The laminate wherein the pressure-sensitive adhesive layer has a light transmittance of 20% or less, and L ^* defined in the L ^* a ^* b ^* color system is 20 or more and 70 or less.

[26] A laminate comprising a metal member (first member), an adhesive sheet, and a light-transmitting member (second member) in this order,

The pressure-sensitive adhesive sheet includes a pressure-sensitive adhesive layer,

The laminate wherein the pressure-sensitive adhesive layer has a light transmittance of 20% or less, and L ^* defined in the L ^* a ^* b ^* color system is 20 or more and 70 or less.

[27] The laminate according to [24] or [26], wherein the metal member is an aluminum member or a stainless steel member.

[28] The metal member includes a processing portion in which processing has been performed,

The laminate according to [24], [26] or [27], wherein the pressure-sensitive adhesive sheet is attached to a region including a processed portion of the metal member.

[29] The laminate according to any one of [24] and [26] to [28] above, wherein ΔE ^* of the metal member and the pressure-sensitive adhesive sheet is within 5.0.

[30] The laminate according to [25] or [26] above, wherein the light transmittance of the light-transmitting member is greater than 50%.

[31] The laminate according to [25], [26] or [30], wherein the light-transmitting member includes a resin film.

[32] In the pressure-sensitive adhesive layer, any one of [24] to [31] above, wherein a ^* and b ^* defined in the L ^* a ^* b ^* color system are both within the range of -10 or more and +10 or less. Laminates described.

[33] The laminate according to any one of [24] to [32], wherein the pressure-sensitive adhesive layer contains a black colorant as the first colorant and a metal oxide as the second colorant.

[34] The laminate according to the above [33], wherein the content of the metal oxide in the pressure-sensitive adhesive layer is 1% by weight or more and 6% by weight or less.

[35] The laminate according to [33] or [34], wherein the content of the black colorant in the pressure-sensitive adhesive layer is less than 2% by weight.

[36] In any one of [33] to [35], the weight ratio (C1/C2) of the amount of the first colorant (C1) and the amount of the second colorant (C2) is in the range of 0.01 to 0.30. Laminates described.

[37] The laminate according to any one of [24] to [36] above, wherein the pressure-sensitive adhesive layer is an acrylic pressure-sensitive adhesive layer containing an acrylic polymer as a base polymer.

[38] The laminate according to any one of [24] to [37] above, wherein the pressure-sensitive adhesive layer has a thickness in the range of 10 to 50 μm.

[39] The laminate according to any one of [24] to [38] above, which is a substrate-free double-sided adhesive pressure-sensitive adhesive sheet containing the pressure-sensitive adhesive layer.

[40] The laminate according to any one of [24] to [39] above, which is used for a portable electronic device.

[41] An adhesive composition containing at least two types of colorants.

[42] The pressure-sensitive adhesive composition according to [41], wherein the content of the colorant in the pressure-sensitive adhesive composition is 1% by weight or more and 10% by weight or less based on solid content.

[43] The pressure-sensitive adhesive composition according to [41] or [42], wherein the pressure-sensitive adhesive composition contains a black colorant as the first colorant and a metal oxide as the second colorant.

[44] The pressure-sensitive adhesive composition according to [43], wherein the content of the metal oxide in the pressure-sensitive adhesive composition is 1% by weight or more and 6% by weight or less based on solid content.

[45] The pressure-sensitive adhesive composition according to [43] or [44], wherein the content of the black colorant in the pressure-sensitive adhesive composition is less than 2% by weight based on solid content.

[46] In any one of [43] to [45], wherein the weight ratio (C1/C2) of the amount of the first colorant (C1) and the amount of the second colorant (C2) is in the range of 0.01 to 0.30. The adhesive composition described.

[47] The pressure-sensitive adhesive composition according to any one of [41] to [46], wherein the pressure-sensitive adhesive composition contains an acrylic polymer as a base polymer.

[48] In any one of the above [41] to [47], which is used to form a pressure-sensitive adhesive layer having a light transmittance of 20% or less and L ^* defined in the L ^* a ^* b ^* color system of 20 or more and 70 or less. The adhesive composition described.

[Example]

Hereinafter, several examples relating to the present invention will be described, but the present invention is not intended to be limited to those shown in the examples. Incidentally, in the following description, "parts" and "%" used as units of content or added amount are based on weight unless otherwise specified.

<Evaluation method>

[Light transmittance]

The light transmittance [%] of the pressure-sensitive adhesive layer and the pressure-sensitive adhesive sheet is the light transmittance in the thickness direction (light transmittance at a wavelength of 550 nm) of the pressure-sensitive adhesive layer and the pressure-sensitive adhesive sheet peeled from the release liner, respectively, and based on JIS K 7136: 2000, It is measured using a commercially available transmittance meter. As the transmittance meter, a spectrophotometer manufactured by Hitachi, Ltd. (equipment name "U4150 type spectrophotometer") or an equivalent thereof is used.

[Light Reflectance]

The light reflectance (%) of the surface of the pressure-sensitive adhesive layer and the surface of the pressure-sensitive adhesive sheet was measured using a commercially available spectrophotometer, and light having a wavelength of 550 nm was separated from the release liner on one surface of the pressure-sensitive adhesive layer or pressure-sensitive adhesive sheet (light reflectance measurement surface). It can be obtained by irradiating to the surface and measuring the intensity of the light reflected from the irradiated surface. As the spectrophotometer, a spectrophotometer manufactured by Hitachi, Ltd. (equipment name "U4150 type spectrophotometer") can be used, for example.

[L ^* a ^* b ^* value]

Each value of L ^* a ^* b ^* in the pressure-sensitive adhesive layer and pressure-sensitive adhesive sheet is measured using a color difference meter based on JIS Z8781-4:2013. Specifically, after attaching one adhesive surface of the pressure-sensitive adhesive layer or the pressure-sensitive adhesive sheet to a stainless steel plate (SUS304BA board), the other pressure-sensitive adhesive layer or the pressure-sensitive adhesive sheet (measurement target surface) was subjected to L It can be obtained by measuring each value of ^* a ^* b ^* . As the color difference meter, "CR-400" (trade name) manufactured by Konica Minolta Co., Ltd. or an equivalent product thereof is used. In the case of a single-sided adhesive sheet, the measurement may be performed by placing the back surface (non-adhesive surface) of the single-sided adhesive sheet on the stainless steel plate.

[180 degree peel strength (adhesion)]

Under a measurement environment of 23° C. and 50% RH, a PET film having a thickness of 50 μm is attached to one side of the adhesive side of the double-sided pressure-sensitive adhesive sheet for backing, and cut to a size of 25 mm in width and 100 mm in length to prepare a measurement sample. With respect to the produced measurement sample, in an environment of 23° C. and 50% RH, the adhesive surface of the measurement sample is pressed against the surface of a stainless steel plate (SUS304BA plate) by making a 2 kg roller reciprocate once. After leaving it for 30 minutes in the same environment, the peel strength (adhesive force) [N/25 mm] was measured using a universal tensile compression tester in accordance with JIS Z 0237: 2000 under the conditions of a tensile speed of 300 mm/min and a peel angle of 180 degrees. Measure. As the universal tension/compression tester, for example, "Tensile/Compression Tester, TG-1kN" manufactured by Minebea Co., Ltd. or an equivalent product thereof is used. In addition, in the case of a single-sided pressure-sensitive adhesive sheet, it is unnecessary to line the PET film.

[Shear adhesion]

A pressure-sensitive adhesive sheet (double-sided pressure-sensitive adhesive sheet) is cut into a size of 10 mm x 10 mm to prepare a measurement sample. Under an environment of 23° C. and 50% RH, each adhesive surface of the measurement sample is superimposed on the surface of two stainless steel plates (SUS304BA plates), respectively, and compressed by a 2 kg roller reciprocating once. After leaving it for 2 days in the same environment, shear adhesion [MPa] is measured using a tensile tester under conditions of a tensile speed of 10 mm/min and a peel angle of 0 degree. In the case of a single-sided adhesive sheet (single-sided adhesive sheet), the non-adhesive surface of the sheet may be fixed to the stainless steel sheet with an adhesive or the like, and the measurement may be carried out in the same manner as above. As a tensile tester, a universal tensile compression tester (product name "TG-1kN", manufactured by Minebea) can be used.

[Concealment of the processing object]

The concealment of the adherend to be processed by the pressure-sensitive adhesive sheet is evaluated by the following method. Each value of L ^* a ^* b ^* (L ^* ₁ , a ^* ₁ , b ^* ₁ ) measured for the pressure-sensitive adhesive layer (adhesive sheet) and each value of L ^* a ^* b ^* of the adherend material (L ^* ₀ , a ^* ₀ , b ^* ₀ ) are determined as ΔL ^* , Δa ^* , and Δb ^* , respectively. Here, ΔL ^* =L ^* ₁ -L ^* ₀ , Δa ^* =a ^* ₁ -a ^* ₀ , Δb ^* =b ^* ₁ -b ^* ₀ . The obtained ΔL ^* , Δa ^* , Δb ^* are expressed as:

ΔE ^* = [(ΔL ^* ) ² + (Δa ^* ) ² + (Δb ^* ) ² ] ^1/2

, and the color difference ΔE ^* with the adherend is obtained as an evaluation index of the concealability of the adherend. In the evaluation described later, L ^* ₀ , a ^* ₀ and b ^* ₀ are the values measured for the adherend material (stainless steel sheet), L ^* (40.5), a ^* (0.02) and b ^* (- 1.59) was adopted. When the color difference ΔE ^* is within 20, it is judged as 'G (good)', when the color difference ΔE ^* is within 5.0, it is judged as 'E (excellent)', and when ΔE ^* exceeds 20, it is judged as 'P( poor)'. In addition, the said color difference (DELTA)E ^* 5.0 is defined as the color difference which can be recognized as substantially the same when compared with time in ISO compliant Japan color sheetfed printing 2011.

<Example 1>

(Preparation of acrylic polymer)

95 parts of n-butyl acrylate (BA) and 5 parts of acrylic acid (AA) as monomer components and 233 parts of ethyl acetate as a polymerization solvent were added to a reaction vessel equipped with a stirrer, thermometer, nitrogen gas inlet pipe, reflux condenser and dropping funnel. This was added and stirred for 2 hours while introducing nitrogen gas. After removing oxygen in the polymerization system in this way, 0.2 part of 2,2'-azobisisobutyronitrile (AIBN) was added as a polymerization initiator, and solution polymerization was carried out at 60°C for 8 hours to obtain a solution of acrylic polymer A. The Mw of this acrylic polymer A was about 70×10 ⁴ .

(Preparation of adhesive composition)

To the acrylic polymer solution, 20 parts of terpene phenol resin as a tackifying resin, 3 parts of an isocyanate crosslinking agent and 0.01 part of an epoxy crosslinking agent as a crosslinking agent are added to 100 parts of the acrylic polymer A contained in the solution, and further a first colorant Carbon black particles (manufactured by Dainichi Seikagyo Co., Ltd., trade name "ATDN101 Black", average particle diameter: 350 nm) as (black colorant) were 0.29% in the pressure-sensitive adhesive layer, and the second Titanium oxide (TiO ₂ ) particles (product name 'WHITE PASTE R-2228', manufactured by Dainichi Seika Kogyo Co., Ltd., average particle diameter: 50 nm) as a colorant (metal oxide) were added to the pressure-sensitive adhesive layer to be 4.52%, and stirred and mixed to obtain an adhesive. A composition was prepared. As a terpene phenol resin (tackifying resin), trade name "YS Polyster T-115" (manufactured by Yasuhara Chemical Co., Ltd., softening point: about 115°C, hydroxyl value: 30 to 60 mgKOH/g) was used. As the isocyanate-based crosslinking agent, "Coronate L" (manufactured by Tosoh Corporation, 75% ethyl acetate solution of trimethylolpropane/tolylene diisocyanate trimeric adduct) was used as the isocyanate-based crosslinking agent. As the epoxy-based crosslinking agent, trade name "TETRAD-C" (manufactured by Mitsubishi Gas Chemical Co., Ltd., 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane) was used.

(Manufacture of adhesive sheet)

The above adhesive composition was applied to the release surface of a polyester release liner (trade name 'Diafoil MRF', manufactured by Mitsubishi Polyester) having a thickness of 38 μm, and dried at 100° C. for 2 minutes to form an adhesive layer having a thickness of 35 μm. did To this pressure-sensitive adhesive layer, the release side of a polyester release liner (trade name "Diafoil MRF", manufactured by Mitsubishi Polyester Co., Ltd.) having a thickness of 25 µm was bonded. In this way, a substrate-free double-sided pressure-sensitive adhesive sheet having a thickness of 35 탆 and both surfaces protected by the two polyester release liners was obtained.

<Example 2>

A pressure-sensitive adhesive composition according to this example was prepared in the same manner as in Example 1 except that the content of carbon black particles in the pressure-sensitive adhesive layer was changed to 0.30% and the content of titanium oxide particles was changed to 3.46%. A substrate-free double-sided pressure-sensitive adhesive sheet was prepared.

<Example 3>

Acrylic polymer B was synthesized in the same manner as in the synthesis of acrylic polymer A except that the monomer composition was changed to 95 parts of 2-ethylhexyl acrylate (2EHA) and 5 parts of AA, thereby obtaining a solution of acrylic polymer B. To this acrylic polymer solution, 20 parts of terpene phenol resin as a tackifying resin, 10 parts of acrylic oligomer, and 3 parts of isocyanate crosslinking agent and 0.03 part of epoxy crosslinking agent as crosslinking agents were added to 100 parts of acrylic polymer B contained in the solution. Further, 0.32% of carbon black particles as the first colorant (black colorant) and 3.15% of titanium oxide particles as the second colorant were added in the pressure-sensitive adhesive layer, and stirred and mixed to prepare an adhesive composition. As the terpene phenol resin, isocyanate-based crosslinking agent, epoxy-based crosslinking agent, carbon black particles, and titanium oxide particles, the same types as those used in Example 1 were used.

As an acryl-type oligomer, what was prepared by the following method was used. Specifically, in a reaction vessel equipped with a stirrer, a thermometer, a nitrogen gas inlet pipe, a reflux condenser, and a dropping funnel, 95 parts of cyclohexyl methacrylate (CHMA) and 5 parts of AA, 10 parts of AIBN as a polymerization initiator, and polymerization After adding toluene as a solvent and stirring in a nitrogen stream for 1 hour to remove oxygen in the polymerization system, the temperature was raised to 85°C and reacted for 5 hours to obtain an acrylic oligomer having a solid content concentration of 50%. Mw of the obtained acrylic oligomer was 3600.

A substrate-free double-sided pressure-sensitive adhesive sheet having a thickness of 35 µm was obtained in the same manner as in Example 1 except for using the obtained pressure-sensitive adhesive composition, both surfaces of which were protected by the two polyester release liners.

<Example 4~5>

A pressure-sensitive adhesive composition according to each example was prepared in the same manner as in Example 1 except that titanium oxide particles were not used and the content of carbon black particles in the pressure-sensitive adhesive layer was changed to 2.00% (Example 4) and 0.40% (Example 5). And, using the pressure-sensitive adhesive composition, a base-free double-sided pressure-sensitive adhesive sheet according to each example was prepared.

<Example 6~9>

The content of carbon black particles in the pressure-sensitive adhesive layer was 0.11% (Example 6), 0.10% (Example 7), 0.13% (Example 8), and 0.09% (Example 9), and the content of titanium oxide particles was 5.31% (Example 6). , 5.59% (Example 7), 4.56% (Example 8), and 5.59% (Example 9), except that each was changed in the same manner as in Example 1 to prepare an adhesive composition according to each example, and each A substrate-free double-sided pressure-sensitive adhesive sheet according to the example was produced.

Table 1 and Table 2 show the outline of the adhesive according to each example, the light transmittance, the light reflectance, each value of L ^* a ^* b ^* , the adhesive force, the shear adhesive force, and the evaluation results of the concealability of the adherend to be processed.

[Table 1]

[Table 2]

As shown in Tables 1 and 2, in the PSA sheets according to Examples 1 to 3 and Examples 6 to 9, the light transmittance of the PSA layer is 20% or less, L ^* is within the range of 20 to 70, and the adherend to be processed is The evaluation result of the concealability of was a pass. On the other hand, in the PSA sheets according to Examples 4 and 5, the light transmittance of the PSA layer was 20% or less, but L ^* was outside the range of 20 to 70, and the evaluation result of the concealability of the adherend was disqualified.

From the above results, according to the PSA sheet containing the PSA layer having a light transmittance of 20% or less and L ^* defined in the L ^* a ^* b ^* color system of 20 or more and 70 or less, the surface to which the PSA sheet is attached is processed. It turns out that good concealment property can be exhibited also with respect to an adherend.

As mentioned above, although the specific example of this invention was demonstrated in detail, these are only examples and do not limit the scope of a claim. The technology described in the claims includes various modifications and changes of the specific examples exemplified above.

1, 230: adhesive sheet
1A: adhesive surface, first adhesive surface
1B: adhesive surface, second adhesive surface
21: adhesive layer
21A: adhesive surface, first adhesive surface
21B: adhesive surface, second adhesive surface
31, 32: release liner
41: first member
42: processing part
45: second member
50: laminate
100: portable electronic device
200: display device
220: display unit
240: support

Claims (13)

A non-substrate double-sided adhesive pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer,
The pressure-sensitive adhesive layer has a light transmittance of 20% or less, and L ^* defined in the L ^* a ^* b ^* color system is 20 or more and 70 or less,
The pressure-sensitive adhesive layer includes a black colorant as a first colorant and a metal oxide as a second colorant. According to claim 1,
In the PSA layer, a ^* and b ^* specified in the L ^* a ^* b ^* color system are both within a range of -10 or more and +10 or less. According to claim 1 or 2,
The content of the metal oxide in the pressure-sensitive adhesive layer is 1% by weight or more and 6% by weight or less, the pressure-sensitive adhesive sheet. According to claim 1 or 2,
The pressure-sensitive adhesive sheet wherein the content of the black colorant in the pressure-sensitive adhesive layer is less than 2% by weight. According to claim 1 or 2,
A weight ratio (C1/C2) of the amount (C1) of the first colorant and the amount (C2) of the second colorant is in the range of 0.01 to 0.30. According to claim 1 or 2,
The pressure-sensitive adhesive layer is an acrylic pressure-sensitive adhesive layer containing an acrylic polymer as a base polymer. According to claim 1 or 2,
An adhesive sheet that is adhered to a region including a processed portion of a processed metal member. According to claim 1 or 2,
An adhesive sheet used for joining metal members in portable electronic devices. A display device including a display unit including a cover member and an organic EL unit, and a support unit, comprising:
An adhesive sheet is bonded to the support portion,
The pressure-sensitive adhesive sheet is a substrate-free double-sided adhesive pressure-sensitive adhesive sheet including a pressure-sensitive adhesive layer,
The pressure-sensitive adhesive layer has a light transmittance of 20% or less, and L ^* defined in the L ^* a ^* b ^* color system is 20 or more and 70 or less,
The display device, wherein the pressure-sensitive adhesive layer contains a black colorant as a first colorant and a metal oxide as a second colorant. A laminate comprising a metal member and an adhesive sheet,
The pressure-sensitive adhesive sheet is a substrate-free double-sided adhesive pressure-sensitive adhesive sheet including a pressure-sensitive adhesive layer,
The pressure-sensitive adhesive layer has a light transmittance of 20% or less, and L ^* defined in the L ^* a ^* b ^* color system is 20 or more and 70 or less,
The laminated body in which the said adhesive layer contains a black colorant as a 1st colorant, and a metal oxide as a 2nd colorant. A laminate comprising a member having light transmission and an adhesive sheet, comprising:
The pressure-sensitive adhesive sheet is a substrate-free double-sided adhesive pressure-sensitive adhesive sheet including a pressure-sensitive adhesive layer,
The pressure-sensitive adhesive layer has a light transmittance of 20% or less, and L ^* defined in the L ^* a ^* b ^* color system is 20 or more and 70 or less,
The laminated body in which the said adhesive layer contains a black colorant as a 1st colorant, and a metal oxide as a 2nd colorant.
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